Time – Invest it now or waste it later

Time – Invest it now or waste it later

Invest your time

Time is one of those things that you cannot get back once it is gone. This is the same for you as a mechanic as it is for your customers. Many times, customers come in and we want to get them out as quickly as possible. This means that mistakes can happen and you need to be aware of this. Many times we end up wasting time by cutting corners and unintentionally missing a problem.

 

Cutting corners to save time

Time is perhaps the most valuable commodity we have. For some reason we don’t always use it wisely. Most quality work involves investing some additional time  before any payback can be realized. Many technicians know this yet they come up with excuses like “That sounds great, BUT I don’t have the time”. It is true that the stresses of the shop environment can lead technicians to cut corners. This is a problem because when too many corners get cut the cost of accomplishment can quickly rise. It is important to be careful and try to recognize which things are top priority. It then becomes a simple matter of taking the time to focus on those things first.

Don't cut corners sign

Meeting Demands in a Constructive Way

Balancing the demands of high volume and quality work is not an easy task. When considering this, it is important to remember the saying “Nothing good in life is ever easy”. It is no different in this scenario. Accomplishing both goals in a consistent manner is what truly sets the TOP shops apart from the rest of the pack.

The brake inspection process is a perfect example. It can be easy to skip the pretest drive, forget to do an under-hood check, or pull only 2 or 3 wheels without pulling the calipers. Many mechanics do this because they think that by taking these and other shortcuts it will help the shop’s busy volume. While id does help reduce “dead” bay time the comebacks caused by these shortcuts end up costing the technician both in credibility and financial success.The few extra minutes it takes to turn an incomplete inspection into a complete one pays big dividends.  By taking the time to do this, you gain more legitimate profit per job and less unproductive bay time. Here are some real life examples of how shortcuts cost money:

Examples

The image on the right shows what a shop found when they went to bleed a system out. After selling $600 worth of wheel based brake work they found this. The problem? They never opened the hood until after the work was completed. The system had been contaminated with power steering fluid and required an additional $800! Imagine being in the manager’s shoes telling the customer what happened, it would be embarrassing. It is important to ask yourself wether or not the time saved on any given “corner cut” is worth it? The answer to that question will almost alway be “no.”

sized wheel cylinder

Seized cylinders

Swollen Diaphram

The two seized wheel cylinders on the left were found on a customers third visit. The customer stopped by each time for the same issue, warranty of the loaded calipers. The front brake pads on the vehicle only lasted only 2,000 miles. On the third set of calipers, the shop finally took the time to do it right. After checking if the wheel cylinder pistons were actually moving, they quickly found the problem. This vehicle should be braking with a 60/40 front to rear split but because of the seized wheel cylinders it had zero rear braking. The braking balance on this vehicle was 100/0!

Premature pad wear

Premature pad wear, over heating, drag and brake noise can all be related to proper caliper function. Even with this correlation, many shops don’t check the function of the caliper during the inspection. Very few shops ever take time to pull a caliper during the inspection. Not doing so can lead to missing both pad and caliper related conditions. The image below shows some of what can be missed by NOT pulling the caliper.

missed conditions of a bad brakepad

Failure to pull calipers will cost the shop the brake job in many cases. The friction and caliper will look good on the outside but have hidden problems. Either the shop will give them a clean bill of health and miss the sale or it could raise costs after the job is sold. If the shop sells based on the outside inspection and then finds other needs after the job is started it can get pretty ugly going back to the customer with additional costs.

Conclusion

A good technician should be able to perform a complete 4-wheel inspection on a typical vehicle in 15 to 25 minutes without missing anything. This is about 10 minutes more than what is being spent currently in most shops. That extra 10 minutes will work for you or against you depending on how you use it. The additional time spent to do a thorough inspection, should yield happier and safer customers because you are going to find things you may not have found otherwise.

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Rust and Runout

Rust and Runout

Problem:

High speed pulsation, usually above 35mph, occurring shortly after brake job or tire service is performed (usually between 3,000 and 6,000 miles).

Cause:

One or more of the rotors installed with excessive runout. Generic specification being used by domestic OEMs is .002”. Excessive runout causes disc thickness variation (DTV) over time. The average for most vehicles is 3,000 to 6,000 miles. This number can vary up or down based on the variables involved.

Figure 28.1 Jacking

Rust on the hub’s mating surface is a leading cause of runout. The rust can form to a point where it actually pushes the rotor away from the hub even with the wheel bolted on (See Figure 28.1). This process has been termed “jacking”. It works much the same way as a tree root under a side walk. There are tremendous forces involved as the rust “grows” between the rotor and hub.

Solution:

Cleaning of the rotor and hub’s mating surfaces is a critical part of the brake job. The hub to rotor mating surface must be free of rust or runout induced DTV can occur shortly after the brake job. As little as .001” of rust at the outside edge of the hub will result in .002” to .004” of runout.

The method used to clean the hub will depend on the severity of the rust buildup. The hub’s mating surface can be a difficult surface to clean due to the wheel studs. The area between the wheel stud and hub centering flange is the most difficult area to gain access to. Here are the best methods to clean the hub’s mating surface.

Method 1 – Mild rust build up:

1. Use an angle grinder equipped with a scotch brite disc to clean the majority of the surface area. Get as close to the studs as possible and change the disc when needed.

2. Finish the process by using the tool shown in Figure 28.2 to clean the area around the studs. This tool fits over the wheel stud to allow easy cleaning of the hard to reach area of the hub. Figure 28.3 shows the finished result.

Figure 28.2 OTC Tool

Figure 28.3 OTC Tool Hub

Method 2 – Severe rust buildup:

The hub shown in Figure 28.4 will not be able to be cleaned effectively using the steps outlined above. The end result would look something like Figure 28.5. The OTC tool does NOT work on mild to heavy rust. It has a tendency to polish the rust instead of removing it. The most effective method is to use the steps below:

Figure 28.3 Rusty Hub

Figure 28.5 Polished Rust

1. Abrasive blasting is the most effective method for rust removal. There is a specialized blast cabinet available that allows cleaning of the hub while it is still on the vehicle. The tool uses a drawstring boot to allow the unit to be used on the vehicle as shown in Figure 28.6.

Figure 28.6 Rust Buster

2. Figure 28.7 shows the finished product. This is the same hub shown in Figure 28.4. This hub will not be the source of rust induced runout. While there are other methods that can be used to clean rusty hubs the method described above are the most effective. Other methods can be time consuming, yield a lower quality job and may not result in all of the rust being removed.

Figure 28.7 Finished Product

How to Verify Accuracy of Setup on Bench Lathe

How to Verify Accuracy of Setup on Bench Lathe

Problem:

Bench lathe induced runout is a leading cause of runout induced DTV pulsation comebacks.

Cause:

There are three main reasons for bench lathe induced runout. They are:

  • Arbor runout
  • Adapter condition
  • Not verifying accuracy of setup

This tip will cover the process called “Scratch Cut” which is used to verify accuracy of setup.

Solution:

All rotors and drums machined on a bench lathe should be scratch cut before machining. This is necessary to verify the accuracy of the lathe setup. Skipping this step can lead to machining runout into the rotor. The process of verifying the setup is commonly referred to as “Scratch Cut”.

  1. Position the bits approximately .” away from the outside edge of the rotor.
  2. Bring the outside bit in until it just touches the rotor. While holding the outer knob place the inner dial on zero. On lathes without this feature take note of the dial reading.
  3. Back the cutting tip away from the rotor a small distance and turn the lathe off.
  4. Observe the scratch cut. If the scratch cut is at least 50% around the rotor proceed with the machining process (Figure 27.1). If the scratch cut is less than 50% then the setup needs to be verified (Figure 27.2).

    Figure 27.1 More Than 50 Percent

    Figure 27.2 Scratch Cut First Cut Less Than 50 percent

  5. Two things will cause a scratch cut of less than 50%. The first is the rotor has runout and needs to be machined.
  6. The second is a problem in the setup. Adapter cleanliness, arbor runout and tightening of the arbor nut are the main causes of setup problems.
  7. To verify the setup loosen the arbor nut. While holding the inner and outer adapter rotate the rotor 180 degrees. Retighten the arbor nut. This process changes the relationship of the rotor and adapters.
  8. Turn the lathe on and then move the twin cutter in or out a small distance.
  9. Make a second scratch cut by turning the dial to zero. On lathes without this feature turn the dial into the same number as the first scratch cut. This process makes each scratch cut the same depth which makes comparing the cuts easier.
  10. Back the cutting tip off a small distance and turn the lathe off. Compare the two scratch cuts. If the problem is in the rotor the cuts should on top of one another (Figure 27.3).

    Figure 27.3 Scratch Cut Second Matching First

  11. A setup problem will cause the second cut to be in a different position from the first (See Figure 27.4). If this is the case disassemble everything and check for cleanliness, correct adapters and for nicks on the mating surfaces (See Figure 27.5). Do not proceed with the machining process until the scratch cuts are in the same position. Doing so will induce runout into the rotor.

    Figure 27.4 Scratch Cut Not Matching

    Figure 27.5 Clean Surfaces

Bonus Tip:

EVERYTHING machined on a bench lathe should be scratch cut to verify accuracy.

Read last week’s post on Bench Lathe Adapter Service.

Bench Lathe Adapter Service

Bench Lathe Adapter Service

Problem:

Reoccurring pulsation complaints (high speed pulsation occurring after 3,000 to 6,000 miles)

Cause:

Bench lathe induced runout

Solution:

Preventing the majority of bench lathe setup problems is a relatively easy process. It involves the following steps:

  1. Arbor Shaft Runout: Measure arbor runout and correct if necessary (Figure 26.1). The typical specification for arbor runout measured near the end of the arbor is .002”. If the runout is outside of acceptable, remove and clean the mating surfaces. If this doesn’t correct it consult your lathe manual.

    Figure 26.1 Arbor Shaft Runout

  2. Arbor Face Runout: Measure the arbor face runout (Figure 26.2). The typical specification for this measurement is .0005”. Correction of excessive arbor face runout will have to be performed using the lathe manufacturer’s procedures.

    Figure 26.2 Arbor Face Runout

  3. Hubless Adapter Arbor Mating Surface: The adapter show in Figure 26.3 is typical in many shops. Hubless adapters rely on the mating of the surface shown in Figure 26.3 and the arbor face to be accurate and true. With the buildup shown in Figure 26.3 it would be impossible for an accurate setup with this adapter.

    Figure 26.3 Dirty Adapter Face

  4. Correcting Arbor Mating Surface: To clean the small mating surface, place a piece of sandpaper on a flat surface and run the adapter’s small face up and down a few times while applying even pressure. The end result should look like Figure 26.4. Don’t worry about pits or indentations, these won’t effect the mating.

    Figure 26.4 Clean Adapter Face

  5. Indexing Adapter to Lathe: (This step is optional if the arbor face runout was .0000”.) If the arbor face runout was greater than zero then the hubless adapters will have to be indexed to the lathe before continuing. Some adapters have index marks cast into them while others don’t. If there is no index mark use a file to make an index mark on the edge of the small mating surface as shown in Figure 26.5.

    Figure 26.5 Adapter Index Mark

  6. Preparing Adapter for Machining: Install the adapter on the lathe and position the twin cutter to enable machining of the large mating surface as shown in Figure 26.6. Sometimes it will be necessary to remove the opposite tool holder to achieve the proper clearance.

    Figure 26.6 Twin Cutter Setup

  7. Machining Large Mating Surface: Remove only as much material as necessary to achieve a 360 degree cut. This usually only requires .002” to .005”. Make a slow cut to machine the large mating surface. This process makes this mating surface true to the lathe as shown in Figure 26.7.

    Figure 26.7 Finished Product

  8. Optional Adapters: The same procedure can be used on the optional adapters available for most bench lathes such as the composite rotor adapter shown in Figure 26.8.

    Figure 26.8 Other Adapters

The average bench lathe setup will take between 1 to 2 hours to perform the procedures listed above on all the adapters in the shop. Once this procedure is performed all that is necessary it to keep the small and large mating surfaces clean and free of nicks and burrs. If the arbor face had runout and index marks were used then the adapter and arbor index marks should be aligned each time the adapters are used.

Even after this procedure has been done it is still necessary to check the setup. This is done by performing what is known as “scratch cut”.

Brake Lathe Arbor – Checking & Correcting Runout

Brake Lathe Arbor – Checking & Correcting Runout

Problem:

Bench lathe induced runout is a leading cause of runout induced DTV pulsation comebacks.

Cause:

There are three main reasons for bench lathe induced runout. They are:

  • Arbor runout
  • Adapter condition
  • Not verifying accuracy of setup

This tip will cover checking and correction of the lathe’s arbor. If the arbor has excessive runout (> .002”), then everything machined on that lathe will have some runout.

Solution:

Proper care of the arbor and periodic measurement of arbor runout will eliminate the arbor as a cause of lathe induced runout. Follow the steps below to check and correct arbor runout.

Measuring Arbor Runout: (Ammco lathe shown, others similar)

  1. Lathes using tapered arbors use witness marks to indicate the most accurate fit of arbor to spindle. These marks are made at the factory after the arbor is matched to the lathe. Verify these marks are aligned as shown in Figure 25.1

    Figure 25.1 Witness Marks

  2. Position the dial indicator as shown in Figure 25.2.

    Figure 25.2 Dial Indicator Setup

  3. Use the draw bar nut to rotate the spindle while watching the dial indicator. It is best to use a socket and ratchet when performing this step. Use a smooth 360 degree rotation for the most accurate measurement. If arbor runout is within specifications (generic no more than .002” with the closer to zero the better) no service is needed. If outside of specifications follow the steps below.

Correcting excessive arbor runout:

  1. Remove arbor. Inspect arbor and spindle taper(s) for chips or rust buildup (Figure 25.3). The tapered surfaces of the spindle should be cleaned using a fine to medium steel wool. The arbor’s tapered surface(s) can be cleaned using a wire wheel.

    Figure 25.3 Rusted Taper

    NOTE: Do NOT use sandpaper, emery cloth or anything that could remove metal. The taper surfaces determine the arbor’s fit and changing them in any way could result in permanent damage to the accuracy of these surfaces.

  2. Use a clean rag to wipe all mating surfaces before installing the arbor. Put a light coat of WD40 or similar treatment on the tapered surface(s) before installing. This will help prevent rusting.
  3. Align the witness marks and tighten the arbor nut or draw bar to specifications. This is usually around 50-60ft lbs.
  4. Repeat steps 1 to 3 under “Measuring runout” above to check arbor runout. If less than .002” process completed. If not, follow the steps below to determine the cause.

Determining source of excessive arbor runout:

  1. Rotate arbor until dial indicator is at its highest reading. This is the point of greatest runout. Use a magic marker to mark the point on the arbor as shown in Figure 25.4. This mark will be used to determine if the arbor is the source of the any excessive runout.

    Figure 25.4 Arbor High Spot

  2. Loosen the arbor and rotate it 1/8 of turn clockwise and tighten the drawbar. Measure arbor runout.
  3. If run-out is .002″ or less, make a mark on the arbor at the spindle witness mark.
  4. If more than .002″ runout is indicated, loosen the drawbar, rotate the arbor 1/8 turn in the spindle and retighten the drawbar.
  5. Recheck the run-out.
  6. If it is still more than .002” repeat step 4 and 5 until .002” or less runout is achieved. Then mark the arbor to the spindle witness mark.
  7. If the runout is still greater than .002” after the arbor has been rotated 360 degrees, rotate the arbor until the dial indicator shows the maximum runout reading. Check to see if the magic marker reference mark placed on the arbor in step 1 is aligned with the dial indicator plunger. If the two are aligned, the arbor is bent and will have to be replaced.

Note: Some older lathes may not have a witness mark. Dial indicate the arbor and mark both the arbor and spindle.

How to Diagnose Excessive Disc Thickness Variation (DTV)

How to Diagnose Excessive Disc Thickness Variation (DTV)

Problem:

Determining if one or more rotors has excessive DTV

Cause:

The average specification for disc thickness variation (DTV) is .0005” (See Figure 24.1). The maximum allowable variation in thickness on a rotor is 5 ten thousandths of an inch. This dimension is too small to measure accurately at the shop level.

Figure 24.1 Average DTV

Most publications give instructions for measuring DTV. The typical steps involve making 6 to 8 measurements at a certain distance from the edge of the rotor and then comparing these measurements to one another. If they vary by more than .0005” the rotor has excessive DTV. Measurements this small can only be accurately done in a laboratory environment.

Solution:

The only effective method to determine if one or more rotors has excessive DTV is by the symptom it produces. Excessive DTV is the leading cause of high speed pulsation complaints.

Excessive DTV is usually more pronounced when stopping from speeds above 35mph. The changing thickness of the rotor causes the caliper piston to move in and out. The movement of the caliper piston causes fluid movement in the hydraulic system which is felt in the brake pedal.

If the vehicle is exhibiting high speed pulsation then one or more of the rotors has excessive DTV. If the vehicle is disc/drum then both front rotors should be serviced according to their thickness and condition.

If the vehicle is equipped with 4 wheel disc brakes use the location of the vibration to help pinpoint front or rear. If the steering wheel and/or dashboard shake in addition to the brake pedal the problem is related to one or both front rotors. If the vibration is in the seat or floorboard it is most likely a rear problem. DTV is more common on front disc brakes than rear.

BONUS TIP:

You CANNOT measure thickness variation at the shop level. You must rely on the symptom it produces to know whether you have it.

How to Measure Rotor Runout

How to Measure Rotor Runout

Problem:

Accurately measuring installed runout

Cause:

Runout measurement is not being performed on a regular basis so many technicians do not know how to perform it.

Solution:

The dial indicator is used primary to measure rotor runout. In can also be used to measure arbor runout on the bench lathe, wheel bearing play and hub runout. Accurate measurements depend on proper use of the tool. The following steps outline the proper use of the dial indicator.

Attach flexible mount to vise grips. There are three mounting holes in the mounting block. The end one is usually the best one to use when possible.

Note: Make sure the flexible mount is screwed in tightly to the vise grip mount.

Locate a solid mounting point on the vehicle. Some examples would be the caliper mounting bracket, pad rails, lower strut mounting bolt, steering arm. Do not mount to anything that is not stationary in reference to the rotor (See Figure 23.1).

Figure 23.1 Vise Grip Mounted

On hub style rotors there must not be any bearing play. If excessive play is present adjust bearing before measurement. Hubless rotors have to be secured with spacers and lug nuts. On a 5 lug hub use at least 3 lug nuts. On a 4 lug hub use 2 opposite lugs with spacers. Where possible the lug nuts should be installed backwards with the flat sides against the spacers.

Attach the dial indicator by loosening the clamp screw. Tighten the clamp screw to a point where the dial indicator can be moved around easily.

With the red handle pointing directly in line with the base of the flexible mount , take the slack out of the flexible mount by turning the adjusting screw clockwise (See Figure 23.2).

Figure 23.2 Indicator Clamp

Locate the dial indicator plunger as shown in Figure 23.3. The tip should be about 1/4” from the edge of the rotor. It should be located on a smooth portion of the rotor. If necessary, take the runout reading on the inner surface of the rotor. The plunger should extend out of the housing and the contact tip should be at a slight angle that is in line with the edge of the rotor (See Figure 23.3).

Figure 23.3 Closeup of Needle

While holding the indicator in this position, rotate the red tension handle 180 degrees or until enough tension is present to hold the unit stationary.

Note: Make sure the tip of the indicator is screwed in all the way or vibration will occur during the reading.

Runout can now be taken. Rotate the rotor in the direction the dial indicator tip is pointing.

Watch the needle for the lowest and highest number reached during one revolution of the rotor. The runout is the difference between these two numbers. For example, if the lowest reading was 65 and the highest was 69 the runout is .004” (See Figure 23.4).

Figure 23.4 Reading

If you want to use the zero feature of the indicator rotate the rotor until the lowest reading is obtained. Loosen the set screw and rotate the black dial unit the needle points to zero. Rotate the rotor one complete revolution and note the amount of runout. If done correctly the needle will start and stop at zero without going below it.

Bonus Tip: 

It takes less than 60 seconds to measure rotor runout and KNOW whether the runout will be an issue in that vehicle coming back with a pulsation complaint.

Reoccurring Pulsation

Reoccurring Pulsation

Problem:

High speed pulsation, usually above 35mph, occurring shortly after brake job or tire service is performed.

Cause 1:

One or more of the rotors were installed with excessive runout. Generic specification being used by domestic OEMs is .002”. Excessive runout causes disc thickness variation (DTV) over time. The average for most vehicles is 3,000 to 6,000 miles. This number can vary up or down based on the variables involved.

Cause 2:

Insufficient clearance between inboard and outboard brake pads and rotor’s friction surface. The closer the brake pads are to the rotor’s friction surface the smaller the amount of runout needed to produce disc thickness variation (DTV).

Solution 1:

Rotors must be installed with runout less than vehicle’s specifications in order to eliminate runout induced DTV. There are 2 options to perform this.

Option 1: Use an on-the-car lathe to machine the rotors true to the hub. Make sure to index the rotor to the hub if removing it after the machining process. Make sure to properly torque the wheels using the method described in step 6 below.

NOTE: When performing on-the-car machining on vehicles equipped with ABS make sure none of the machining chips accumulate on the magnetic sensor tip. This could trigger false activation of the ABS or fault codes. See Figure 22.1

Figure 22.1 Lathe Chips

Option 2: If using a bench lathe to perform off the vehicle machining follow these steps:

  1. If resurfacing the rotor(s) use proper machining techniques and make sure the lathe is in good working condition. On hubless rotors make sure to clean the mating surfaces with an appropriate tool. Scratch cut all rotors to ensure accurate setup.
  2. Clean the rotor before installing on vehicle to prevent machining dust from contaminating brake pads.
  3. Before installing hubless rotors, clean the hub mating surface using an appropriate tool(s). Failure to properly clean this surface can prevent achieving the proper installed runout.
  4. When installing new or machined hubless rotors the installed runout should be checked. Using spacers on the studs tighten all lugs to the proper torque using the correct sequence. Measure runout. If runout is not less than manufacturer’s specification index the rotor on the hub to achieve the lowest amount of lateral runout.
  5. Before indexing mark the high spot on the rotor and hub using a magic marker or paint stick as shown in Figure 22.2. Indexing involves removing the rotor and rotating it one or two lugs and reinstalling. Repeat this until the installed runout is below specification. If runout is out of specifications and does not change as the rotor is rotated check to see if the high spot moves with the rotor or stays with the hub. This will identify the cause of the runout.

    Figure 22.2 Indexing

  6. Properly torque the wheel lugs using either a hand torque wrench or torque stick sockets. When torquing wheels use a step torque process. To step torque the lugs tighten all lugs to half the normal torque using proper sequence and then fully torque lugs using same process. Make sure your impact has been calibrated before using torque sticks.

Solution 2:

Look closely at Figures 22.3 & 22.4. Both rotors shown have the same runout but what they don’t have is the same gap between the pads and rotor. The gap between the pads and rotors in Figure 22.3 is much smaller than that of Figure 22.4. The smaller the gap the more sensitive the vehicle will be to runout induced DTV. Remember the wear of the high and low spots occurs during both brake apply and release. If something in the caliper assembly is preventing a full or complete release of either the outboard or inboard pad that wheel will be more susceptible to this problem. Improper release of either pad could make even those rotors at or below .002” prone to this problem.

Figure 22.3 Small Pad to Rotor Gap

Figure 22.4 Large Pad to Rotor Gap

Effective inboard pad release will be effected by two types of conditions. The first of these involves how well the piston releases. A piston that does not return as far as it should reduces the gap between the inboard pad and rotor. Mileage, brake fluid condition, dust boot seal integrity all can impact the piston’s ability to release properly. The second condition that can effect the release of the inboard pad involves how easy the pad can move in relationship to the caliper mounting bracket, knuckle or slide rails. If the inboard pad binds then complete release will not take place.

Outboard pad release can be impacted by two categories of failures as well. The most common of these is the slide hardware. If the caliper housing is not free to move on its mounting hardware then outboard pad release will be effected. The other category is the same as for inboard pad release, that is anything causing the outboard pad to bind where it contacts the bracket, knuckle or slide rails.

Nothing new about what impacts inboard or outboard pad wear but understanding its influence on the issue of runout induced DTV is a fairly new concept. The moral of the story is short cutting quality brake work impacts more than just pad life. The old “pad slap” has more chances to come back and haunt you than what you might have considered. Remember just because the caliper applies and releases doesn’t guarantee its doing it as effectively as it should. Look at the big picture when doing your brake inspection. A few more minutes covering the details up front will pay big dividends in the long run. A saying I like to use sums it all up – “I would rather be paid today for what is wrong with the vehicle than have to give it away tomorrow”.

More Info: The fact that excessive runout is the leading cause of reoccurring pulsation should not be anything new. The principal is easy, too much runout on fixed bearing vehicles causes the high and low spot of the rotor to scrape against the pads. This scraping occurs during both non-braking and braking. Over time the high and low spots are worn thinner than the other portions of the rotor. This difference in thickness is known as disc thickness variation or DTV (See Figure 22.5). It is also called parallelism. The two friction surfaces of a rotor are supposed to be parallel to one another to within a certain tolerance. The average value for this specification is .0005”. As little as 5 ten thousands of an inch or another way to say it would be ó of one thousandth of an inch tolerance is all that is allowed.

Figure 22.5 Disc Thickness Variation (DTV) Views

If DTV is in excess of acceptable limits the thin spots pass between the pads during brake apply causing the caliper piston must move out to take up the gap. The thick portions of the rotor push the piston back. The in and out movement of the piston causes the pedal to pulsate especially at speeds above 35mph. What has been stressed is the importance of getting the rotor’s installed runout to acceptable levels. Most domestic OEMs are agreeing that this amount is .002” or less. While this is definitely the most important aspect of curing the reoccurring pulsation it is not the only thing to consider. There are other factors that will contribute to the vehicle’s sensitivity to this.

Bonus Tip: 

Discard the myth that reoccurring pulsation complaints are caused by warped rotors due to overheating.

Rotor & Drum Specification Accuracy

Rotor & Drum Specification Accuracy

Problem:

Not all of the specifications provided are 100% accurate.

Cause:

Consolidated specification sources often make mistakes when compiling the information from the various manufacturers.

Solution:

Verifying accuracy of rotor and drum specifications.

A close look at Figure 21.1 shows the 1998 Buick Skylark vehicle listed having different machine to specifications. Depending on the circumstances using the wrong specifications could result in machining a rotor that should have been replaced or selling one that could of been serviced.

Figure 21.1 Rotor Specs

You are making some pretty important decisions based on the specifications you get out of your specs book – you need to make sure they are accurate. Read our previous post on Rotor & Drum Specification Issues as well.

The best method is to find two specifications from different information providers that are the same. The most accurate sources are the rotor itself, information providers such as Mitchell or All Data, and specifications provided by the parts manufacturers.

Rotor & Drum Specification Issues

Rotor & Drum Specification Issues

Problem:

Determining a rotor’s or drum’s serviceability based on available specifications.

Cause:

Many manufacturers do not supply both machine to and discard thickness

Solution:

No Machine to Specification Listed

Many vehicles no longer provide a machine to specification. This does not mean the rotor is not serviceable. Most of these rotors are allowed to be machined to the discard specification. This is not a practical procedure in a shop environment. This is especially true in the states where there are safety inspections performed. It is possible to perform a brake job and have the vehicle fail a state inspection only a couple of months after the brake job.

Figure 20.1 shows an example of this. In this example no machine to specification is given. Instead a “NS“ is listed. The “NS” is short for “Not supplied by manufacturer”.

Figure 20.1 No Machine To

In this case the machine to is calculated by added .015” to the discard specification provided. In the case of the 98 to 2000 Mountaineer the discard listed is .980”. Adding .015” to this would yield a machine to thickness of .995”.

No Discard Specification provided

In Figure 20.2, no discard specification is given. Instead a footnote number is listed. The footnote listed is number 2 which can be found at the end of the make section. Footnote 2 says:

“Discard when thickness is smaller than the minimum machining specification”

20_2_footnote example_rgb

This means the discard and machine to specification are the same number. This would not be practical for the customer. If the rotor were machined down to the machine to it would go beyond service in a very short period of time. Another brake inspection or a state inspection would result in the rotor being under specifications after just being serviced. The industry has adopted the position of creating a revised machine to specification by adding .015” to the number provided. In the case of the 2001-99 Cougar the machine to listed is .874”. Adding .015” to it will bring the revised machine to up to .889”. This is number you would use to determine whether the rotor can be machined or not. The .015” allows for normal rotor wear during the life of the friction material.

NOTE: Although it is best to use the aftermarket approach, it is acceptable to machine these rotors down to the machine to specification listed. The invoice should be marked “rotors at minimum machining/discard” to avoid future problems.

The same holds true for brake drums. There is no drum discard specification provided for the vehicles in the highlighted box. Instead, a footnote number 3 is listed and that footnote says:

“Discard when diameter is greater than the maximum machining specification”

This means the maximum machining diameter and discard diameter are the same for these vehicles. If the drum were machined up to the machine to it would go beyond service in a very short period of time. Another brake inspection or a state inspection would result in the drum being over specifications after just being serviced. The industry has adopted the position of creating a revised machine to specification by subtracting .015” from the number provided. In the case of the 2001-99 Cougar the machine to listed is 9.040”. Subtracting .015” from this value would result in a machine to specification of 9.025”. This is the number you would use to determine whether to machine the drum or not.

Bonus Tip:  ‘NS” does NOT mean “Not Serviceable” as some technicians have been led to believe. It means “Not Supplied”.

How To Determine if A Rotor Can Be Serviced

How To Determine if A Rotor Can Be Serviced

Problem:

Whether a rotor can be serviced is based on its dimensions and condition. The decision to service or replace the rotor may be based on incorrect information leading to over or under selling.

Cause:

The dimensions of a rotor determine whether it can be machined, replaced or in some cases left alone. Not understanding the meaning of the dimensions involved in making these decisions can lead to a rotor being machined when it shouldn’t be or a new rotor sold when the old rotor was still serviceable.

Solution:

Understanding all of the critical dimensions of a rotor will allow accurate determination of the rotor’s condition and what type of recommendation should be made. Here is a description of the important dimensions of a rotor:

Nominal Thickness:

Nominal thickness is the thickness of the rotor when it is new. This thickness is not usually used on a daily basis but is listed in most specification books.

Machine to thickness:

This is the thinnest a rotor can be machined to and still be put back into service. The purpose of having a machine to thickness is to provide enough rotor material to last the life of one set of pads. The assumption is that if the pads are replaced and the rotors are over machine to they should not experience enough wear to allow them to go below discard thickness through the life of that set of pads. The average difference between nominal and machine to thickness is .050“ to .060“. The typical difference between machine to and discard (explained below) is .015“. See Figure 19.1.

Figure 19.1 Rotor Dimensions

There is a common myth concerning what are usually called throwaway rotors. The myth states that most rotors on late model vehicles have no meat on them and are not meant to be machined or can‘t be. This is not true. Again, the average rotor provides .050“ to .060“ with some giving as much as .100“ between nominal and machine to thickness. With the average machining taking off .010“ to .015“ there is usually always room for one machining and sometimes 2. The only true throwaway rotors are marked like the one in Figures 19.2 & 19.3. The footnote (3) on this BMW denotes the rotor should be replaced not machined. True throwaway rotors are marked in this fashion.

Figure 19.2 BMW Throwaway Rotor Footnote

 

Figure 19.3 BMW Throwaway Rotor Listing

Discard Thickness

The discard thickness of a rotor is the thickness at which the rotor should be replaced. The common understanding of the definition of discard thickness is that it is a heat related dimension. It is generally understood that if a rotor is at or below discard thickness it cannot dissipate the heat generated. This is not correct. Discard thickness is the thinnest a rotor can wear to so that if the brake pads wear to nothing the caliper piston won‘t fall out of the caliper housing. It has nothing to do with heat. See Figure 19.4.

Figure 19.4 Discard Thickness

This definition makes sense if you apply it to what most technicians have experienced over the years. The average technician has serviced many vehicles with a rotor at or below discard and the vehicle stopped fine. The technician usually doesn‘t know the rotor is at or below discard until they measure the rotor and compare the measurement to the specifications.

Parallelism (Disc Thickness Variation, DTV)

The two friction surfaces of a rotor are designed to be parallel to one another within a certain specification. The allowable tolerance is known as parallelism. It is also known as the rotor‘s disc thickness variation or DTV. See Figure 19.5.

Figure 19.5 DTV Views

Other rotor factors

A common question presented about rotors involves the thickness of one friction disc to the other on vented rotors as shown in Figure 19.6. There is not a published specification for the allowable tolerance for the difference in the thickness of one disc to the other. Some rotors are actually designed intentionally with different thickness discs. It is generally accepted that small differences are acceptable and are either intentional or a result of manufacturing variations.

19.6 Friction Discs

When machining a rotor, the thickness of one friction disc to the other should be taken into consideration. For example, if a rotor is gouged on one friction surface due to metal to metal contact with the brake pad but not the other, it could be possible to machine the gouge out and the rotor still be over machine to thickness. The problem would be that the gouged friction disc would be considerably thinner than the opposite disc. When faced with this situation common sense is the only guide. If the gouge is deep enough to result in having to remove a considerable amount of material it is probably best to replace the rotor.

Corrosion and rust can also have an impact on the rotor‘s ability to function correctly. Figure 19.7 shows a rotor that has clogged vent holes due to rust buildup. This rotor is thick enough to machine but the rust will prevent proper cooling. Likewise the rotor pictured in Figure 19.8 has experience enough corrosion to actually weaken its structural integrity.

19.7 Plugged Fins

Figure 19.8 Structural Damage

The rust has eaten away at the thickness of the cooling fins. This condition could result in the two halves of the rotor separating resulting in a catastrophic brake failure. Always perform a thorough visual inspection of the rotor to determine its condition and serviceability.

Rotor thickness is not very exciting but crucial in doing a good brake job.

What To Do About Brake Noise

What To Do About Brake Noise

Problem:

Vehicles returning with complaints of brake noise

Cause:

One thing that both customers and technicians have in common is they both hate dealing with brake noise. Customers find brake noise annoying and embarrassing. Technicians find brake noise frustrating and unproductive. Unfortunately, both groups find brake noise all too common. Most shops that perform brake service will tell you that brake noise represents the most common reason for brake comebacks.

Brake noise is the layman’s description of the symptom. Brake noise is actually vibration that is occurring at a frequency that is audible to the human ear. All brakes make noise or vibrate. The difference is that most brakes operate at a frequency that we can’t hear.

Solution:

Well, then, its simple, to prevent or fix brake noise all we have to do is make sure the brakes operate (or vibrate) at the right frequency. In theory it is that simple but in real life there is often much more to it than meets the eye. There are many variables involved in the equation that can result in brake noise. Understanding these variables is the starting point of preventing brake noise complaints.

Notice I used the word “prevent” not fix. This should be our primary goal. If we get a handle on how to prevent noise complaints from occurring then we will be better able to handle any comebacks. Most brake noise complaints involve disc brakes so we are going to focus our attention on disc brakes. As the brake pedal is applied and the disc brake pads are squeezed against the rotor, vibration is produced. The points where the vibration takes place are pictured in Figure 18.1. Vibration can occur between the:

  1. Pads and rotor
  2. Pads and caliper
  3. Caliper and knuckle or mounting bracket
  4. Pads and knuckle or mounting bracket
  5. Caliper and mounting hardware

    Figure 18.1 Brake Noise

The number of points where the vibration occurs will vary with the type of disc brake used. The type of disc brake will also determine which causes will be more common. As you can see from the list, the prevention of most brake noise complaints will boil down to performing quality brake service and using quality parts. We will discuss each of these potential problem spots and cover what should be done to prevent them.

• Rotor Finish – the smoothness of the friction surface of the rotor is important in preventing brake noise complaints. This is especially true right after a brake job is performed. The smoother the surface at the start of a brake job the lower than chances for brake noise.

• Friction material – It is commonly felt that the brake pad is the leading culprit in creating brake noise. While in some cases this is true it is not a blanket statement that can be applied to all cases. If you have access to Mitchell On Demand or All Data you might want to take some time and look through some of the TSB’s (Technical Service Bulletins) dealing with brake noise that have been published by the various OEMs. If you do, you would see that changes in brake friction material is often used to help combat brake noise complaints. If you take a closer look, you would see that it is not the only method used. How does this relate to you and the friction material you are using? My position on aftermarket friction and brake noise is this – if you use a quality product from a reputable supplier then you should not have noise problems with MOST vehicles. Quality pads should be designed after the OEM pad. This means they should have shims, tapered edges or dust slots if the OEM pads were equipped with these features.

  Pad shims – Pad shims are used as an insulator between the pads and caliper. This serves to change the frequency of the vibration so brake noise is eliminated. The shims could be attached to the brake pad or they could be supplied as separate parts. Make sure your replacement pads are shimmed to match the OE pads and when servicing vehicles with separate shims either reuse the shims if in good condition or replace them. Do not reuse shims where the protective coating has worn off or if the shims are rusting and flaking. Do yourself a favor and add the cost of replacing the shims into your estimate now instead of giving them away later.

  Pad hardware – It used to be that imports were the only vehicles using pad anti-rattle hardware but now disc brake assemblies similar to that shown in Figure 18.2 have become the standard on many domestic vehicles. The pads “snap” into the caliper mounting bracket and are held in place by various clips. The caliper straddles the assembly and serves only to provide the squeezing of the pads against the rotor. The caliper mounting bracket absorbs all of the braking force and maintains the pad’s position. The anti-rattle hardware applies tension to the pads so they fit snugly against the mounting bracket. These clips are essentially small springs made of stainless steel. They are subjected to the same heating and cooling as rear brake hardware. How many of you are strong believers that the brake shoe hardware should be changed with each set of shoes? What’s the difference with the front hardware? Simply cleaning and reinstalling it won’t be good enough in many cases. Some add an extra step of “re-tensioning” the clips by bending the tabs slightly. This may work for a short time but won’t provide a long-term solution. Suggesting the replacement of this hardware with each pad replacement is something you should consider. The hardware can be pricey and you should explain to the customer why you are suggesting it. If they decline and have a noise problem later then you are in a better position than if you said nothing about the hardware.

Figure 18.2 Caliper and Mounting Bracket

  Caliper hardware – Most vehicles use floating calipers. The rubber bushings or sleeves in these calipers allow the caliper to move freely on brake apply and release. They wear over time and can increase the chances for brake noise. Careful inspection should be done and replacement should be suggested or required based on the findings. If the bushings or sleeves are too loose fitting the caliper will be allowed to move too much (See Figure 18.3). This will increase the chances for a brake noise problem especially if other problems are present. Again, if the customer declines the service, mark the invoice accordingly. If a noise comeback occurs, you will have set the groundwork for what needs to be done. It’s a better position to be in then having nothing to fall back on.

18_3_worn rubber_rgb

Figure 18.3 Rubber Busing is Worn

  Cleaning & lubing – The amount and type of cleaning you will have to do will vary with the type of vehicle being serviced and the area of the country you live in. Some vehicles have only a few key areas that need to be cleaned when servicing the disc brakes while others require considerable more effort. If you work in the south or out west then you won’t have to deal with too much rust like those of us in the snow belt. For more information on cleaning and lubing see our blog post.

  Pad staking – Some outboard pads are designed to be “staked” to the caliper. This staking holds the pad firmly in place and prevents vibration. Older domestic RWD vehicles use outboard pads that stake to the caliper using small tabs as shown in Figure 18.4. This style of pad is best staked off of the caliper. Bend the tabs on the pad until a press fit is needed to install it. Use a pair or channel locks to press it onto the caliper using a piece of cardboard to protect the friction material. Some General Motors vehicles require a different procedure to stake the outboard pad. The pads pictured in Figure 18.5 are first installed on the vehicle. Next a chisel is driven between the hat of the rotor and the base of the pad to hold the pad against the caliper. Now, have an assistant apply and hold the brake pedal. This will hold the pads in place while you perform the staking. The tabs should be bent over at about a 45-degree angle. Release the brakes and check the tightness. No movement should be felt between the pad and caliper.

Figure 18.4 Stake Off Caliper

Figure 18.5 Stake On Caliper

  Pad break in – Starting the mating of the pads to the rotor and getting the brake job off on the right foot is critical to the long term success of the brakes. See our blog post for more information on the proper break-in procedures.

My experience is if you apply the information above and the information contained in the related articles mentioned you will eliminate 8 of 10 brake noise comebacks. If that is the case what do you do with the other 2? This is when you consider the friction material as the possible culprit. If I am involved in a brake noise comeback, I first look at whether any of the steps above have been skipped or not performed properly, in other words was a quality brake job performed. If the answer is yes, then I consider an alternate pad.

Brake pad noise is one of those things that annoys everybody so it is better to do the best job possible to prevent it and we hope this post helps you with that.

What is Friction Break In and How To Do It

What is Friction Break In and How To Do It

Problem:

Brake noise complaints or lack of stopping power shortly after brake job

Cause:

Not performing a proper break-in after performing brake service

Solution:

Once the job has been completed, a test drive should be performed. The test drive has two goals. The first is to make sure the brake system is operating properly. The other reason a test drive is performed involves mating the pads to the rotors. This can be called “break in” or “burnishing” the pads. It doesn’t matter what you call it, it matters that you do it. Depending on whom you talk with the number of stops you should make will vary. A good average is 10 to 12. To mate the pads to the rotors make 10 to 12 stops from about 30 to 35 mph down to about 10 mph. Allow about 30 seconds between stops for cooling.

When you deliver the vehicle to the customer, advise them not to do any severe braking for the first couple of hundred miles. This includes towing or hauling and having them anticipate their stops when possible.

Management is trying to influence two types of customers. One group of customers feels the best check for quality brake work is to go out an lock em up. Too many of this type of stop right after the job is done can have irreversible effects on the performance of the brake job. The other group of customers are those that will leave your shop with the brand new brake job and go on vacation. Not catching that customer who is leaving for vacation the day after your brake job with everything but the kitchen sink in tow can cost you big time. Talk to and educate your customers, it will benefit both of you in the long run.

Some OEMs endorse the same steps on their new cars. Figure 17.1 shows the new vehicle break-in page from a owners manual on a late model GM vehicle. You can see the same steps as stated above covered in points 2 & 3.

Figure 17.1 New Vehicle Break In

At times it will not be practical to perform the second part of the break-in process. Asking fleet customers to not tow or haul for 200 miles is not practical. In these cases, try and at least double the number of stops taken in the first step to bring the process closer to completion.

Remember that proper friction break in is part of any quality brake job.

What are some of your thoughts on brake pad break-in? We would love to hear them and any other thoughts you might have on what we should include in our Tech Tricks Tuesday posts.

Slide Rail Repair

Slide Rail Repair

Problem:

Worn slide rails on vehicles equipped with pad slide rails (See Figure 16.1)

Figure 16.1 Worn Slide Rail

Cause:

The slide rails wear due to the tremendous forces during braking and lack of lubrication. The constant force of the brake pads being pushed into the slide rails during braking combined with the constant back and forth movement of the brake pads causes “dimples” to wear in the most used areas.

Solution:

In theory the only fix to this problem is to replace the part with the worn slide rails. Depending on the application this will either be the caliper mounting bracket or the entire steering knuckle. Neither of these repairs is practical.

The slide rails can be repaired following the steps below:

  1. Clean the slide rail surfaces down to bare metal taking care not to remove good material. (See Figure 16.2

    Figure 16.2 Cleaned Side Rail

  2. Using a MIG welder fill the worn spots making sure to use the necessary settings to get good penetration. Try to avoid building the area up to high. The more buildup the more work. (See Figure 16.3)

    Figure 16.3 Welded Slide Rail

  3. Using an angle grinder with an abrasive sanding disc rough in the repaired area. Use the surrounding surfaces as a reference.
  4. When close, use a Scotch-Brite disc to perform the finish work. The area can be checked using a straight edge. (See Figure 16.4)

    Figure 16.4 Completed Side Rail

  5. Check the final repair by sliding the pad the full length of the slide rails while checking for binding.

BONUS TIP:

Using this process will save your customer money, provide a legitimate profit for the shop, and restore the knuckle to like new condition.

Next week we will discuss Friction Break In and last week we discussed How to Fix Binding Calipers on Ford Light Trucks. Enjoy the reading material and keep coming back for more Tech Tricks Tuesday.

How To Fix Binding Calipers on Ford Light Trucks

How To Fix Binding Calipers on Ford Light Trucks

Problem:

Calipers binding causing premature outboard pad wear

Cause:

This problem can have two different causes. They are:

  1. Using petroleum based lubricants on this design caliper can cause the rubber in the keepers to swell. Swelling of the rubber will cause the caliper to bind on release.
  2. Buildup of rust and corrosion between the caliper/keeper/knuckle or failure to properly clean the mating surfaces of the caliper/keeper/ knuckle.

Solution:

The solutions to each of the causes listed above are:

  1. Ford states in TSB 98-5A-13 to use only a high quality silicone lubricant when servicing these trucks. Silicone will not effect the rubber and serves to repel the water.
  2. Whenever servicing the brake pads on this type of caliper make sure to clean all mating surfaces before applying the lubricant.

More Info:

Many Ford light trucks and SUVs use the sliding caliper pictured in Figure 15.1. When performing service on this type of caliper it is important to use the correct type of lubricant.

Figure 15.1 Ford Sliding Caliper

Ford service information states to use only a high quality silicone lube. Use of any petroleum based lubricant will cause the rubber core of the keep to swell. The swelling will restrict caliper movement and result in outboard pad wear. Moly-lube, anti-seize, white lithium grease and most other commonly used lubricants are petroleum based and should never be used on brake rubber parts. Use of the silicone lube will not only prevent damage to the rubber core of the keeper but silicone also repels water.

Remember to keep coming back for our Tech Tricks Tuesday Blog Posts and to read those past posts to stay up to date on tricks that we have learned from our years of experience.

How to Clean and Lubricate Brake Parts to Help Prevent Comebacks

How to Clean and Lubricate Brake Parts to Help Prevent Comebacks

Problem:

Premature wear and brake noise comebacks

Cause:

Sometimes the cause relates to the quality of the cleaning and lubing

Solution:

The amount and type of cleaning you will have to do will vary with the type of vehicle being serviced and the area of the country you live in. Some vehicles have only a few key areas that need to be cleaned when servicing the disc brakes while others require considerable more effort. If you work in the south or out west then you won’t have to deal with too much rust like those of us in the snow belt. We commonly have to deal with brackets that look like the one in Figure 14.1.

Figure 14.1 Corroded Mounting Bracket

Failure to clean the highlighted surfaces will cause nothing but problems. When cleaning, make sure only to remove the corrosion and not to remove good metal. The bracket in Figure 14.2 has had a number of the surfaces damaged by too aggressive of cleaning using an angle grinder. This can allow too loose of a fit for the pads or cause other related problems.

Figure 14.2 Damaged Mounting Bracket

A commonly missed surface, especially where rust is common, are the caliper “ears” that support the outboard pad. These flat surfaces can have considerable rust buildup over time as shown in Figure 14.3. Another source of buildup can come from the use of some of the brake quiet products on the market. If there are remnants of these products on the caliper‘s mating surface it will reduce the surface contact and could increase the chances for brake noise. Failure to clean these surfaces will not allow the outboard pad to sit squarely against the caliper increasing the chances for vibration.

Figure 14.3 Corroded Ears

Once all surfaces have been cleaned they need to be lubed. There are many choices out there for brake lube and as many opinions of which ones to use. I recommend the use of a high quality moly-lube on all metal to metal surfaces and a high quality silicone lube on all metal to rubber parts. The reason I like the silicone on metal to rubber is that silicone repels moisture and if used properly it will form a nice moisture barrier. There are some basic rules of thumb to follow when using both lubricants. One is – “a little goes a long way” or conversely – “too much is not always a good thing”. For example, the bracket in Figure 14.4 should first have a light film of moly-lube applied as shown. Next, install the anti-rattle hardware and apply a thin film to the surfaces that contact the brake pads as in Figure 14.5. The bracket can now be installed on the vehicle.

Figure 14.4 Lubed Mounting Bracket

Figure 14.5 Lubed Mounting Clips

How about the brake pads? What if anything should be applied to the back of the pads? There are a number of different products available for this task so which one should you use? Again, most experts agree that a thin film of moly-lube is the best method to combat brake noise. The key here is to apply it where it will make a difference. Rather than apply it to the entire back of each pad try this, apply a thin layer to each caliper “ear” and then a small circle on the inboard pad where the piston contacts the pad as shown in Figure 14.6. What about pads that already have shims? Should anything be done to them? I say yes, do the same thing. On vehicles with multilayered shims put a thin layer between each layer. If you ever noticed this is how most of these vehicles come from the factory.

Figure 14.6 Lubed Brake Pads

Keep coming back to our blog to get more Tech Tricks Tuesday info and you can read our previous Blog Posts to help solve those brake system problems you might be having.

Outboard Pad Wear and/or Brake Pull

Outboard Pad Wear and/or Brake Pull

Problem:

Brake lead or pull and/or outboard premature pad wear on Chevy & GM trucks

Cause:

Insufficient clearance between caliper and steering knuckle (See Figure 13.1). Heat expansion causes caliper to bind in knuckle causing side to side brake imbalance. This condition will also prevent proper outboard pad release and will result in premature outboard pad wear.

Figure 13.1 GM Caliper Clearance

Solution:

If one of these trucks presents itself with the symptom of brake lead or pull and/or premature outboard pad wear the caliper to knuckle clearance should be checked. Follow the steps below:

1. Measure the clearance individually and add the two values together. Total clearance should be greater than .010”. If clearances are not within tolerances go to next step.

2. Correct clearances by filing metal off of knuckle stops to achieve a total clearance between .010” and .024” (See Figure 13.2). Do NOT remove material from the caliper.

Figure 13.2 Checking GM Caliper Clearance

As always, check out our recent Tech Trick Tuesday Blog Posts.

Stoplight Switch Adjustment & Pad Wear

Stoplight Switch Adjustment & Pad Wear

Problem:

Premature pad wear ranging from mild to severe.

Cause:

While there are many causes of premature pad wear (see our previous Blog posts on this), stoplight switch adjustment can be a common one. It is common enough to have been included in several TSB’s written over the years.

Incorrect stoplight switch adjustment can prevent the brake pedal from returning to a point that allows the cup seals in the master cylinder to open the vent ports as shown in Figure 12.1.

Figure 12.1 Vent Ports

The vent ports allow for fluid expansion when the brakes get hot. If they are not open a residual pressure will be created due to the expanding fluid. The residual pressure will cause the calipers to apply the brake pads slightly and will result in premature pad wear.

Solution:

Vehicles with adjustable stoplight switches will use one of two varieties, adjustable body type or self-ratcheting plunger type. Each is covered below:

Adjustable body type

1. Verify complaint – if there is drag on both front wheels (or all four wheels on 4-wheel disc brake systems) start by loosening the master cylinder away from the vacuum booster by at least .”. This step checks for anything in front of the master cylinder that would be preventing the master cylinder pistons from fully releasing.

2. If the wheels release the stoplight switch adjustment should be checked. Either follow the manufacturer’s procedures or continue with the next step.

3. Duplicate the wheel drag and then loosen the locknut on the stoplight switch. (Figure 12.2)

Figure 12.2 Locknut Style

4. Back the locknuts off to move the stoplight switch away from the brake pedal. Check the brake drag. If wheels released then stop light switch was source of problem. If wheels did not release see page 96 for more information.

5. Adjust the switch by using the locknuts to position it to a point where the plunger is depressed (verify by checking if brake lights are off) making sure pressure is not being applied to brake pedal that would prevent release. (Figure 12.3)

Figure 12.3 Properly Adjusted Switch

Ratcheting Plunger Type (Figure 12.4)

Figure 12.4 Ratchet Style

1. Verify complaint – if there is drag on both front wheels (or all four wheels on 4-wheel disc brake systems) start by loosening the master cylinder away from the vacuum booster by at least. This step checks for anything in front of the master cylinder that would be preventing the master cylinder pistons from fully releasing.

2. If the wheels release, the stoplight switch adjustment should be checked. Either follow the manufacturer’s procedures or continue with the next step.

3. Remove stoplight switch from mounting bracket. This usually involves rotating it 90 degrees in one direction or the other.

4. Pull the plunger out to its full length. (Figure 12.5)

Figure 12.5 Ratchet Style Extended Plunger

5. Insert the stoplight switch back into its bracket while holding the brake pedal in the full released position.

6. Verify proper operation of brake lights.

NOTE: There are other variations of switch adjustments used so it may be necessary to consult the service manual. Always verify proper brake light operation.

NOTE: Cruise control switches can also be the source of the same problem on certain vehicles.

How to Diagnose Side to Side Premature Pad Wear on FWD Vehicles

How to Diagnose Side to Side Premature Pad Wear on FWD Vehicles

Problem:

Inner and outer brake pads on one side wearing out much faster than brake pads on opposite side.

Cause:

The list of possible causes for this pad wear condition is much longer than what most technicians think. Approaching this problem with an incomplete list will result in fixing the symptom not the problem in many cases. The list of possible causes include:

  • Sticking caliper piston on side with problem
  • Check valve brake hose on side with problem
  • Restriction in ABS modulator preventing fluid release on circuit with wear problem
  • Plugged or restricted vent port on circuit with wear problem
  • Opposite side brake hose with restriction
  • Air in opposite hydraulic circuit from problem (i.e. left pads wearing, air is in RF/LR circuit)

    Diagonal Imbalance Fig 11.1

Solution:

Accurate diagnosis of this problem involves 2 components. The first is approaching the problem with a complete list. The second is applying a logical approach to the diagnosis. The first component is listed above. The second component involves the following steps:

  1. Check brake pedal height. Judge pedal against similar vehicles. If pedal has excessive travel or feels spongy bleed and flush entire system paying close attention to the circuit opposite the side with the pad wear.
  2. Test drive vehicle to bring brakes to operating temperature. Raise the vehicle on a lift and check for wheel drag on all four wheels paying close attention to the side where the pad wear is taking place.
    NOTE: If the vehicle cannot be driven due to metal to metal wear the system will have to be restored to a functioning state before complete diagnosis can take place.
  3. If vehicle pulled to side with problem during test drive opposite side brake hose may be restricted. If no other causes of the pull can be determined then brake hose replacement should be suggested.
    NOTE: Many FWD vehicles will NOT pull with a side to side brake imbalance due to what is known as negative scrub radius (See Figure 11.2).  If the vehicle does NOT pull, it does not guarantee the opposite side hose is not restricted. If pressure gauges or clamping plate gauges are available, they should be used to determine side to side braking balance. If not available, a good practice is to perform all other repairs and instruct customer to return in the miles it took to wear the brake pads out for a checkup. Inform them that the opposite brake hose may still be an issue and this step will determine if it is necessary.

Negative Scrub Fig 11.2

Visit us next week as we discuss stoplight switch adjustment and pad wear. If you have missed any of our other Tech Trick Tuesday Blog Posts, you can read about them on our 101 Brake System Tips page.

Policy on Premature Pad Wear

Policy on Premature Pad Wear

Problem:

Customer leaves shop thinking problem is fixed when it is not and returns when brakes are metal to metal.

Cause:

Not taking the steps to insure cause of premature pad wear is actually fixed.

Solution:

Often times the cause of the premature pad wear is obvious and no additional steps should be needed. If the cause is less than obvious or there is any question about whether the repairs that were performed actually will correct the problem, then follow the steps below.

  1. Research how many miles and how long it took to cause the premature pad wear. Take this time and mileage and divide it by 2.
  2. Explain to the customer you would like them to bring the vehicle back for a quick check in the half mileage calculated in step number 1. For example, if the left side pads are wearing out in 5,000 miles, have the customer stop back at 2,500.
  3. After customer leaves, put a reminder to call the customer in your appointment book on the date that represents the time it took the wear to take place.
  4. If the customer doesn’t return by the date in the appointment book, give them a reminder call about the checkup.

Bonus Tip: Using this technique may save you having to replace rotors free of charge.

How to Diagnose Premature Even and Taper Pad Wear

How to Diagnose Premature Even and Taper Pad Wear

We are continuing our discussion on premature pad wear. This week we will be discussing even and taper pad wear. We have discussed several variations of pad wear and this blog post will be the last topic to discuss.

Problem:

One or more brake pads are wearing prematurely or irregularly

Cause:

All pads wearing evenly but prematurely can be caused by the front brakes being overworked due a rear brake problem or front caliper problems or a seized metering valve.

Premature wear of the outboard pad is caused when the outboard pad is not allowed to release off of the rotor properly after the brake pedal is released.

Solution:

Use the following images to help diagnose the cause of the pad wear condition.

Even Pad Wear (All pads worn evenly)

A. Accelerated pad wear (mild)

  • Change in vehicle use from previous set of pads
  • Front to rear brake balance not correct (i.e. rear brake(s) out of adjustment, restricted rear brake hose)
  • Metering valve stuck on open position (Only applies to RWD’s equipped with metering valves)
  • Calipers not allowing proper release of pads due to internal corrosion, seal rollback
  • Inferior friction or friction not suited to vehicle use

Change in Vehicle use from Previous Set of Pads

Front to Rear Brake Balance not correct (i.e. rear brake(s) out of adjustment, restricted rear brake hose)

Metering Valve Stuck in Open Position (Only applies to RWD’s equipped with metering valves)

Calipers not Allowing Proper Release of Pads due to Internal Corrosion, High Mileage OE Calipers, Inefficient Seal Rollback

Inferior Friction or friction not suited to vehicle use

B. Accelerated pad wear (severe)

  • Two foot driving
  • Vehicle being used for commercial application (i.e. delivery, taxi)
  • Venting not being allowed due to plugged or covered vent port in master cylinder

Two foot driving

Vehicle Being used for Commercial Application (i.e. delivery, taxi)

Venting not being Allowed due to Plugged Vent Port in Master Cylinder

Venting not being Allowed due to Covered Vent Port in Master Cylinder

 

Taper Pad Wear

Top to Bottom Taper Wear

Floating/sliding

  • End of pad experiencing wear is binding in bracket or knuckle (can‘t release)
  • End of pad opposite the wear is seized in bracket or knuckle (can‘t apply)

Fixed

  • End of pad experiencing wear is binding in caliper housing
  • End of pad experiencing wear caliper piston not releasing (4 piston caliper)
  • End of pad opposite the wear cannot apply due to seized caliper piston (4 piston caliper)
  • End of pad opposite the wear cannot apply due to pad seized in housing

Inside to Outside Taper Wear

Floating/sliding

  • Brake pad is binding on worn end and can‘t release
  • Brake pad is binding on non-worn end and can‘t apply evenly
  • Rear disc pad with piston locating tab – tab not aligned with piston notch

Fixed

  • End of pad experiencing wear is binding in caliper housing
  • End of pad experiencing wear caliper piston not releasing (4 piston caliper)

Rusting of Caliper Housing Casting Hole

End of pad experiencing wear is binding in bracket or knuckle (can‘t release)

Rear disc pad with piston locating tab – tab not aligned with piston notch

End of pad experiencing wear caliper piston not releasing (4 piston caliper)

This is the final blog post on premature pad wear. We hope that these posts have been informative for you. If you would like to send us feedback on our posts, please visit our Contact Us page and send us a message from there. Next week, we will be discussing a possible policy you should have on premature pad wear and how to help inform your customers so they are happy and safe.

How to Diagnose Premature Pad Wear on RWD and FWD

How to Diagnose Premature Pad Wear on RWD and FWD

We are continuing our discussion on premature pad wear. This week we will be discussing pad wear on rear wheel drive and front wheel drive vehicles. Here is a link to our post from last week on premature inboard pad wear.

Problem:

One or more brake pads are wearing prematurely or irregularly

Cause:

The cause of the pad wear will be based on what type of pad wear is taking place and the configuration of the brake system.

Premature wear of the outboard pad is caused when the outboard pad is not allowed to release off of the rotor properly after the brake pedal is released.

Solution:

Use the following images to help diagnose the cause of the pad wear condition.

  • Front to Rear Split Hydraulic System

    • Piston sticking (symptom – drag)
    • Brake hose on side with problem with check valve condition (symptom – drag)
    • Brake hose opposite side with problem restricted (symptom – pull to side with pad wear)
    • Hydraulic restriction higher than brake hose on side with pad wear not allowing release of pressure (i.e. ABS modulator)

Images for Front to Rear Split Hydraulic Systems (RWD)

9_both_sticking piston_rgb

Piston Sticking (symptom – drag)

9_both_check valve hose_rgb

Brake Hose on Side with Problem with Check Valve Condition (symptom – drag)

9_both_restricted hose_rgb

Brake Hose Opposite Side with Problem Restricted (symptom – pull to side with pad wear)

9_both_abs modulator_rgb

Hydraulic Restriction Higher than Brake Hose on side with Pad Wear not Allowing Release of Pressure (i.e. ABS modulator)

  • Diagonal Split Hydraulic System (All items listed above for Front to Rear Split Hydraulic Systems plus the images below)

    • Piston sticking (symptom – drag)
    • Brake hose on side with problem with check valve condition (symptom – drag)
    • Brake hose opposite side with problem restricted (symptom – pull to side with pad wear)
    • Hydraulic restriction higher than brake hose on side with pad wear not allowing release of pressure (i.e. ABS modulator)
    • Air in opposite hydraulic circuit than side with wear

Images of Diagonal Split Hydraulic Systems (FWD)

9_both_airmc_rgb

Air in Opposite Hydraulic Circuit than Side with Wear (i.e. LF inner and outer pads worn, air in RF/LR circuit)

9_both_vent_rgb

Vent Port Plugged or Covered on Hydraulic Circuit with Pad Wear

The Basics of Rotor Run-out

The Basics of Rotor Run-out

We have been traveling to various customers and trade shows and have neglected our Tech Tricks Tuesday postings. We are two days late this week and will do our best to be better in the following weeks. Because of this, we are giving you an entire blog post with no interruptions.

Many people believe that disc brake rotors can warp during normal service. Tales sometimes, even told by OE Dealerships, will state that you should not apply your brakes. They will also tell you not to drive through a deep puddle when it’s raining because if the rotor is hot from hard application and then gets drenched, it will warp. One national brake trainer’s daughter was actually told this when she brought her new, under warranty, vehicle in because of a pedal pulsation problem.

ROTORS DON’T WARP or at least they don’t under any type of vehicle operation that would enable the vehicle to be safely driven.

What does happen is that rotors will have excessive run out or wobble because they are not operating a right angle in relationship to the hub face. What this means is that every time a portion of the rotor comes around the rotor makes some contact with the pads and wears the rotor thickness away at that point. After this happens for a while and the brakes are applied you feel a pedal pulsation as the pads follow the rotor thickness variation. The pads move in and out causing the pedal pulsation. Changing the rotor with a new one only delays the reoccurrence of the problem. Replacing rotors isn’t solving the problem.

Basics of Rotor Run Out 01

Basics of Rotor Run Out 01

When you apply the brakes you may sometimes feel a pedal pulsation. This condition may be felt under light, medium or hard braking or any one of them. It’s not when the pulsation is felt that is important, it’s the fact that it is present at all.

Basics of Rotor Run Out 02

Basics of Rotor Run Out 02

Sometimes the condition that causes the pedal pulsation, rotor run out, is so severe that you can actually see a portion of the rotor that has been rubbing the pads. Note the rather large area on this rotor that is shinny. This is the spot that is high and rubs the pads when the rotor rotates.

Basics of Rotor Run Out 03

Basics of Rotor Run Out 03

There are specifications published that identify the allowable amount of rotor run out but any run out that causes a pedal pulsation condition is excessive.

Basics of Rotor Run Out 04

Basics of Rotor Run Out 04

The start of the process to identify the cause of the run out condition is mark one stud and the rotor hole that goes over that stud. This is done so you can place the rotor back on the hub in the same place after it is removed for rotor hat inspection reasons.

Basics of Rotor Run Out 05

Basics of Rotor Run Out 05

After removing the tire/wheel and marking a reference stud location next install washers or special pre-load load distribution cones as shown, then torque down the lug nuts to seat the rotor against the hub face. Nest set up a dial indicator as shown and rotate the rotor one full turn. Note the amount of run out shown on the dial indicator. Compare this reading against the specifications published.

Basics of Rotor Run Out 06

Basics of Rotor Run Out 06

This is a close up of the special pre-load spacer. Note the cone shape which accepts the tapered lug nut and the flat outer shoulder that is placed against the outer surface of the rotor hat. Failure to use these spacers or at least large flat washers will lead to improper rotor pre-loading and inaccurate rotor run out measurements.

Basics of Rotor Run Out 07

Basics of Rotor Run Out 07

As part of the identification process of the overall condition of the rotor you should also take thickness measurements in 8 places around the rotor. This established “thickness variation” reference readings that are compared against the specifications published in the brake spec book. If you have rotor run out you usually will also have thickness variation at least in one spot on the rotor.

Basics of Rotor Run Out 08

Basics of Rotor Run Out 08

After you have obtained your run out and thickness specification readings remove the rotor and check the inside of the rotor hat. Rust and scale can easily build up at this location and be the cause of the run out error and accompanying pedal pulsation.

Basics of Rotor Run Out 09

Basics of Rotor Run Out 09

The hub face must also be clean of rust and scale. Use a tool such as the one shown to clean the hub face. Don’t use anything that will remove metal or you may create a condition where you have a rotor run out.

Basics of Rotor Run Out 10

Basics of Rotor Run Out 10

Many technicians along with others recommend applying some grease or anti-size to the hub face to help prevent future rust and scale build up. Some OE manufactures do and have used a lubricant at this location for years while others do not.

Basics of Rotor Run Out 11

Basics of Rotor Run Out 11

It’s a good idea to also clean the outer surface of the rotor hat but remember don’t use anything that will remove metal or you are creating a condition where the wheels clamping force may cause a rotor parallelism or run out condition when the wheel is torqued down to specifications.

Basics of Rotor Run Out 12

The cause of pedal pulsation shouldn’t be a mystery. In addition to checking the rotor run out and rotor thickness variation it is also recommended that you set up your dial indicator and take run out of the hub face. This is easier said than done as the studs make setting up the dial indicator to take a hub run out reading all but impossible.

Hub face run out can be the root cause but the most common condition causing the problem is rust and scale between the hub face and the inside of the rotor hat.

This concludes our Tech Tricks Tuesday Blog Post on the Basics of Rotor Run-out and we hope that you found it useful. If you have any comments, please let us know.

How To Bleed Brakes on a Hybrid Vehicle Part 3

How To Bleed Brakes on a Hybrid Vehicle Part 3

This is part 3 (the final portion) of our Tech Tricks Tuesday on how to bleed brakes on a hybrid vehicle. If you missed last week’s post, you can read it here.

Last week we covered:

  • The history of the Prius used in this write-up
  • Where the master cylinder reservoir is and how to remove the cap
  • The importance of the master cylinder cap
  • A brief overview of the brake system
  • How to properly prime the reverse brake bleeding tool
  • How to get started with reverse bleeding on the hybrid vehicle
  • How to proceed with bleeding the system

This week we will cover:

  • Reason to not shy away from bleeding a hybrid system
  • Potential reason why the fluid is lower in the master cylinder
  • A “best practices” of bleeding using a Phoenix Systems Reverse Bleeder
Hybrid Bleed 22

How to Bleed a Hybrid Step 22

 

Step 22

As before, the master cylinder fluid level rose after bleeding each individual wheel. This is proof that we are achieving fluid flow with the Phoenix bleeder from the wheel hydraulics upstream to the master cylinder.

Hybrid Bleed 23

How to Bleed a Hybrid Step 23

 

Step 23

Some folks shy away from bleeding a brake system on a vehicle when it has a logo on it as shown. Don’t automatically do this. Many hybrids are fairly simple to bleed when using the Phoenix bleeder.

Hybrid Bleed 24

How to Bleed a Hybrid Step 24

 

Step 24

The next vehicle we selected to try bleeding on was this late model Ford Fusion. This vehicle has never had any brake work done on it.

Hybrid Bleed 25

How to Bleed a Hybrid Step 25

 

Step 25

Note the level of the fluid in the master cylinder. It’s lower than it should be. What is the reason? Only two logical possibilities. One it has a leak which it doesn’t and two the friction is worn allowing the pistons to move farther out in the caliper bores which lowers the visible fluid level in the master cylinder. This car is in a fleet and is driven a lot of miles each month by multiple drivers. It’s used daily sometimes for extended trips.

Hybrid Bleed 26

How to Bleed a Hybrid Step 26

 

Step 26

As with most vehicles today the bleeder valves or at least the front wheel bleeder valves are easy to access.

Hybrid Bleed 27

How to Bleed a Hybrid Step 27

 

Step 27

This image shows a rotor on this hybrid with a unusual amount of glaze and material build up (transfer layer). If this wasn’t a hybrid, this may be of some concern but hybrid vehicles use regenerative braking as their primary braking system so the actual wheel brakes really don’t do that much braking.

Hybrid Bleed 28

How to Bleed a Hybrid Step 28

 

Step 28

As shown previously, the tech places his finger over the bleeder valve end of the Phoenix bleeder and compresses the bleeders handle to assure a solid column of fluid prior to putting the rubber end over the bleeder valve and bleeding the system.

Hybrid Bleed 29

How to Bleed a Hybrid Step 29

 

Step 29

This image shows “best practices” of bleeding a wheel using the Phoenix bleeder. The bottle containing the fluid is suspended by a cord and is the lowest component in the system. The bleeder is pointed slightly upward while being used. While not absolutely necessary, some tech feel this assures a solid column of fluid under all bleeding conditions.

Hybrid Bleed 30

How to Bleed a Hybrid Step 30

 

Step 30

This may look like a complex rear caliper/brake system and may also have an electronically actuated parking brake but the system bleeds out like any other caliper system. In the case of most calipers, wheel hydraulics are wheel hydraulics. There is seldom anything very special about them.

Hybrid Bleed 31

How to Bleed a Hybrid Step 31

 

Step 31

As before, you know you had fluid movement upstream by the rise in the fluid level of the master cylinder.

After completing the bleeding of any vehicle check the master cylinder level and adjust the fluid level accordingly. Set the fluid level according to now only the full mark the full hot or full cold mark. What is hot and cold. Use some common sense. If you can touch anything in the engine compartment with any problem it may be considered cold but if you can as you wouldn’t be able to if you just shut it down after a trip it is considered hot.

Can all hybrids be bled without any special procedure or tools? That is a unknown at this time. The thing is that we decided to check out two common hybrid vehicles to see if our bleeder would work on the systems and the answer was found to be yes.

Click here to purchase your Phoenix Systems Reverse Brake Bleeder on our website or at any online retailer.

How To Bleed Brakes on a Hybrid Vehicle Part 2

How To Bleed Brakes on a Hybrid Vehicle Part 2

This is part 2 of our Tech Tricks Tuesday on how to bleed brakes on a hybrid vehicle. If you missed last week’s post, you can read it here.

Last week we covered:

  • The history of the Prius used in this write-up
  • Where the master cylinder reservoir is and how to remove the cap
  • The importance of the master cylinder cap
  • A brief overview of the brake system

This week we will cover:

  • How to properly prime the reverse brake bleeding tool
  • How to get started with reverse bleeding on the hybrid vehicle
  • How to proceed with bleeding the system
Hybrid Bleed 10

How to Bleed a Hybrid Step 10

 

Step 10

Fill the bleeder bottle from a clean unopened container of the correct type of brake fluid. In this case the vehicle specified DOT 3.

Hybrid Bleed 11

How to Bleed a Hybrid Step 11

 

Step 11

Next, put the cap containing the pickup tube onto the bottle.

Hybrid Bleed 12

How to Bleed a Hybrid Step 12

 

Step 12

After tightening the cap, install the return line onto the open cap connection.

Hybrid Bleed 13

How to Bleed a Hybrid Step 13

 

Step 13

Next, prime the hoses by pumping the bleeder handle until you have a solid stream of fluid flowing.

Hybrid Bleed 14

How to Bleed a Hybrid Step 14

 

Step 14

After filling the hose with fluid, attach a bleeder valve end to the hose.

Hybrid Bleed 15

How to Bleed a Hybrid Step 15

 

Step 15

With the bleeder ready to go, loosen the bleeder valve on the first component in the bleed sequence.

Hybrid Bleed 16

How to Bleed a Hybrid Step 16

 

Step 16

Squeeze the handle of the bleeder slightly to be sure the hose and bleeder end is full of fluid then place your finger over the bleeder end.

Hybrid Bleed 17

How to Bleed a Hybrid Step 17

 

Step 17

Place the bleeder valve end of the hose over the bleeder valve, which has been opened and will allow fluid to flow through it.

Hybrid Bleed 18

How to Bleed a Hybrid Step 18

 

Step 18

Pump the handle of the bleeder which forces fluid from the filled bottle through the bleeder and into the hydraulic circuit for this specific wheel.

Hybrid Bleed 19

How to Bleed a Hybrid Step 19

 

Step 19

After bleeding the first wheel in the bleed sequence, the fluid level in the master cylinder reservoir was checked and it was noted that the level was increased from when starting the bleeding. This was proof positive that the fluid was flowing upstream through the system.

Hybrid Bleed 20

How to Bleed a Hybrid Step 20

 

Step 20

The remaining wheels were then bleed flowing the bleed sequence stated in specifications. On the drum brake rear wheels the wheel cylinder bleeder valve was opened and the same procedure as on the front was applied.

Hybrid Bleed 21

How to Bleed a Hybrid Step 21

 

Step 21

After tightening the bleeder valve, the rubber cap was reinstalled. This is important as it prevents moisture from entering the center of the bleed valve and corroding the seat area of the bleeder valve.

This covers this week’s post. Come back next week to discover how to finish up with the bleeding of the hybrid vehicle.

How To Bleed Brakes on a Hybrid Vehicle Part 1

How To Bleed Brakes on a Hybrid Vehicle Part 1

Some people automatically think that bleeding the brakes on hybrid vehicles is difficult, causes secondary service problems, or that doing so requires special OE tools and procedures including special scan tools.

While this may be true in some instances, it is not always true. In an effort to see just how simple or difficult it is to bleed some hybrid vehicles, we recently had the opportunity, on a limited basis, to use the Phoenix Systems Reverse Brake Bleeder on a few hybrid vehicles from a fleet we obtained access to. This fleet has a variety of hybrid vehicles and we chose a first generation Toyota Prius (Gen. I Prius) and a late model hybrid Ford Fusion to work on.

Why these vehicles? Because they are perhaps the two most likely that you may be servicing. The Gen. I Prius has been around long enough to be needing front brake work and the Ford Fusion by it’s shear numbers will be into your shop for brake work sometime in the future.

We were able to use the Phoenix Systems Reverse Brake Bleeder attached at the bleeder valves at the wheels to bleed these two vehicles without doing anything special or using any special procedures. What we did was drive the vehicles into the shop, shut off the vehicles and close the door after removing the keys, lift the vehicle on the lift and attach the Phoenix Systems Reverse Brake Bleeder at each wheel and bleed (move new fluid from the caliper/wheel cylinder) at the wheel up stream to the master cylinder.

You will see that this was successful as the fluid level in the master cylinder was raised after each wheel was bled. Simple, effective, and successful. Will this work on all hybrids? Stay tuned as we continue to expand testing doing service work such as flexible hose replacement, caliper replacement etc. that will allow air into the closed system. What we did prove is that there is a straight fluid flow from the wheels upstream to the master cylinder and that we can move fluid (bleed) from the wheels upstream to the master cylinder on these two types of vehicles.

This week we will cover:

  • The history of the Prius used in this write-up
  • Where the master cylinder reservoir is and how to remove the cap
  • The importance of the master cylinder cap
  • A brief overview of the brake system
Hybrid Bleed 00

How to Bleed a Hybrid Step 00

 

Step 00

This Gen. I Prius has over 250,000 on it. All local in town driving and it’s only on its second set of front brakes. The master cylinders fluid level when it came into the shop was very low. The reason for this was unknown. Also, the fluid appears to never have been tested for corrosion or changed. This alone would be reason do perform a fluid change and bleed out the system.

Hybrid bleed 01

How to Bleed a Hybrid Step 01

Step 01

The master cylinder on the Gen. I Prius is located approximately at the 11 o’clock position in this photo. It’s about the only part of the hydraulic system that is easily visible. All other components of the hydraulic braking system are buried and difficult to see.

Hybrid bleed 02

How to Bleed a Hybrid Step 02

Step 02

This is not the master cylinder on a Prius. Stupid statement? You may be surprised to learn that some folks think it is and then add “you know what”.

Hybrid Bleed 03

How to Bleed a Hybrid Step 03

Step 03

Removing the master cylinder cap is easy. Simply place your fingers under the rubber cap lip and pull out and upward. The reservoir is a white plastic container and has molded in fluid minimum and maximum markings on it.

Hybrid Bleed 04

How to Bleed a Hybrid Step 04

Step 04

The fluid level in the master cylinder was below the minimum mark and the bellows on the cap had expanded as designed. The bellows was pushed back into itself as shown.

Hybrid Bleed 05

How to Bleed a Hybrid Step 05

Step 05

Two things are important to understand about the master cylinder cap on this vehicle. One is that the specifications for the type of brake fluid are molded into the top of the cap. The other item is that you should realize that this cap is not a direct vent type of cap. The bellows which is part of the assembled cap separates the brake fluid from the atmosphere. This is the reason the bellows expanded into the master cylinder when the fluid level dropped. This feature prevents the brake fluid from constantly being in contact with air which contains moisture which would be absorbed by the brake fluid.

Hybrid Bleed 06

How to Bleed a Hybrid Step 06

Step 06

The calipers are conventional in their design and have a standard bleeder valve located at the highest part of the caliper.

Hybrid Bleed 07

How to Bleed a Hybrid Step 07

Step 07

This vehicle had the rubber caps on the bleeder so it was a safe bet they would open easy. Place a six point socket on the bleeder valve and open it with a ratchet.

Hybrid Bleed 08

How to Bleed a Hybrid Step 08

Step 08

The rear brakes on the Prius are drum brakes. The bleeders also opened easy as they also had the OE rubber caps on.

Hybrid Bleed 09

How to Bleed a Hybrid Step 09 

Step 09

A Phoenix Reverse Brake Bleeder and a couple cans of the correct brake fluid is all that was needed to bleed out this Gen. I Prius.

This will cover our portion this week. Come back next week for more information on bleeding a Gen I Prius with a Phoenix Systems Reverse Brake Bleeder.

Read part 2 of our blog post by clicking here.

How to Remove a Rusted Bleeder Screw

How to Remove a Rusted Bleeder Screw

View our most recent post here.

 How to Remove a Rusted Bleeder Screw

If someone says “Pin It”, you may think of a web site that folks sell things on. Nothing could be farther from the truth for our meaning of the term “Pin It”.

What we are talking about is “pinning” or filling the hollow center of a brake bleeder valve when removing it. Why would you want to do this? The answer is simple. This is done to help keep the rusted bleeder screw from breaking when it is “frozen” in the caliper and you are trying to loosen or remove it.

BrakeFree 01

Image 1

 

Image 1

If you take a straw, hold one end, and twist the other end of the straw the center of the straw will twist around itself. Think of a hollow bleeder valve with the bottom of the bleeder valve rusted into the caliper. Think of what happens to the bleeder valve when you apply force with a wrench trying to loosen it.

BrakeFree 02

Image 2

Prevent Future Rusted Bleed Screws with the Phoenix Systems USA Made bleed screw caps.

Click Here to Learn More about the bleeder caps

4x4-bleedscrew-cap

Image 2

Now fill the straw with sand or water and repeat this twisting test. You will find that the entire straw now moves. In other words, the straw doesn’t collapse inward onto itself. Pinning a hollow bleeder valve creates the same effect.

BrakeFree 03

Image 3

 

Image 3

Note the amount of rust and scale on the bottom seat area of this bleeder. Bleeder valves freeze up not only on their threaded area but also on the tapered seat at the bottom of the valve.

BrakeFree 04

Image 4

 

Image 4

As mentioned, this is what usually happens to a frozen bleeder valve when it is attempted to be removed. First, the hex flats stripped off then when a locking pliers was used the bleeder collapsed inward on itself breaking in two. The result required caliper replacement to handle the problem.

BrakeFree 05

Image 5

 

Image 5

You can use most anything to fill the center hold of a bleeder valve but a piece of soft welding rod (aluminum welding rod) works very well. Cut the piece slightly longer than the hollow center length.

BrakeFree 06

Image 6

 

Image 6

Insert the “pin” into the bleeders center and tap it downward as far as possible. Don’t worry if it’s a bit long. The idea is to fill the center completely. The soft welding rod will simply flatten itself onto the end of the valve.

BrakeFree 07

Image 7

 

Image 7

Obtain a Phoenix Systems “Brake Free” air hammer tool and place a socket on it of the correct size to fit the bleeder valve. Note: If you use a shallow socket you will apply more force onto the frozen threads and seat than with a deep socket.

BrakeFree 08

Image 8

Free any rusted or frozen bleed screw with Phoenix Systems USA Made BrakeFree Tool

Click Here to Learn More about the BrakeFree Tool.

Screen Shot 2016-03-15 at 1.24.07 PM

Image 8

With the “Brake Free” tool connected to an air hammer insert a #2 Phillips screwdriver or other similar tool through the hole of the “Brake Free” tool. Push downward firmly on the air hammer while pulling the trigger of the air hammer and apply left hand rotational force to the “Brake Free” blade through the Phillips screwdriver.

BrakeFree 09

Image 9

 

Image 9

If you use heat to try to free up the bleeder valve the heat will travel into the caliper body itself and will reach the area housing the caliper square cut seal. This heat may easily cause the seal to have problems. It is never a good idea to heat a bleeder valve to try and free it up. Don’t do it. The negative effects can be safety related.

By using a “BrakeFree” tool along with a good air hammer and a #2 Phillips or other similar drift along with “Pinning” a bleeder screw before applying any force to it, you will find that you will be successful in removing most frozen bleeders.

Granted, you will have to replace the bleeder as it’s almost impossible to get the pin out but that is a small price to pay for successfully remove a frozen bleeder rather than having to replace the entire caliper. We hope that you enjoyed our post on how to remove a rusted bleeder screw.

The “Brake Free” tool can be ordered on our website in our Specialty Tool section.

Prevent Future Rusted Bleed Screws with the Phoenix Systems USA Made bleed screw caps.

Click Here to Learn More about the bleeder caps

4x4-bleedscrew-cap

 

 

 

Brake Hose Service Ideas Part 4

Brake Hose Service Ideas Part 4

We are now on Part 4 of our brake hose service ideas and if you missed part 1, part 2, or part 3, here is a quick recap:

  • How to tell if a brake hose is still able to continue in service or not
  • What cracks mean on a brake hose and if it is serviceable when cracked
  • Is the pull on the vehicle from the brakes or from the brake hoses?
  • What to do with a caliper when servicing the vehicle
  • What heat does to brake hoses
  • Comparison of a crimped hose
  • Petroleum saturation and what happens with that
  • What happens when the wrong brake hose is put on a vehicle
  • Using a valve stem to plug a hole in a caliper
  • What to do when “pinching off” a hose

Idea 17

Another design of a hand tightened line lock. This unit is simply smaller in design.

Brake Hose Service Idea 17

Idea 17

 

Idea 18

This is NOT a proper tool to pinch off a flexible brake hose. This type of tool should never be used and even if you put padding such as a piece of hose over the tools jaw area this tool may easily damage a hose.

Brake Hose Service Idea 18

Idea 18

 

Idea 19

If a hose is pinched off as shown so no fluid and flow through its small internal passage area with a tool as shown damage usually occurs.

Brake Hose Service Idea 19

Idea 19

Idea 20

Note the internal damage from using clamping pliers such as that shown in Pic. 19. This hose will no longer allow the same volume of fluid to flow as the hose on the opposite side of the vehicle. This may give a pull upon initial brake application among other problems.

Brake Hose Service Idea 20

Idea 20

Idea 21

This hose has an internal “flapper valve” type of issue. Brake fluid will flow through the “flapper” but will not easily flow back the other way. This may prevent fluid application or hold fluid onto the caliper depending on the direction of flow in relationship to the “flapper” direction. Was this problem initiated by someone once improperly clamping a flexible brake hose? You don’t really know but it could easily be the cause of the problem.

Brake Hose Service Idea 21

Idea 21

Brake hoses are really not complicated items but a large dose of common sense and understanding must be applied to brake service situations and problems when the brake hose may be the cause of the problem. It is also commonly recommended to replace brake hoses is pairs as if one hose has a service problem the other, unless it was changed individually, may soon follow as its service life has been the same. Pay attention to the tips and recommendations in the previous images and be successful in your brake hose service.

 

 

 

Brake Hose Service Ideas Part 3

Brake Hose Service Ideas Part 3

We are now on Part 3 of our brake hose service ideas and if you missed part 1 and part 2, here is a quick recap:

  • How to tell if a brake hose is still able to continue in service or not
  • What cracks mean on a brake hose and if it is serviceable when cracked
  • Is the pull on the vehicle from the brakes or from the brake hoses?
  • What to do with a caliper when servicing the vehicle
  • What heat does to brake hoses
  • Comparison of a crimped hose
  • Petroleum saturation and what happens with that
  • What happens when the wrong brake hose is put on a vehicle

Idea 12

Note the unusual twist of this hose. Previously when the caliper had been removed and reinstalled the caliper had been rotated 180 degrees when reinstalled. This puts a sharp twist into the hose. Note the end of the hose attached to the caliper and how it appears at the right angle bend.

Brake Hose Service Idea 12

Idea 12

 

Idea 13

When you remove a caliper from a hose attached by a banjo hose fitting use a valve stem to plug the hole. This prevents brake fluid from dripping all over the place and excessive air from entering the brake line.

Brake Hose Service Idea 13

Idea 13

 

Idea 14

No matter what method of pushing the caliper piston back into the caliper bore you use you should open the bleeder and pinch off the fixable brake hose. This prevents the pushing of any contaminants from the caliper back upstream into the brake system components such as ABS control units, a brake valve or the master cylinder.

Brake Hose Service Idea 14

Idea 14

 

Idea 15

Even when you simply push the pads backwards to allow their easy removal from a rotor you should open the bleeder and pinch off the line.

Brake Hose Service Idea 15

Idea 15

 

Idea 16

When pinching off a hose to block fluid flow you should use a properly designed “line lock” type of tool such as the tool shown. Note the tightening is done with a hand turned wing nut, not a hex bolt.

 

Brake Hose Service Idea 16

Idea 16

Keep coming back each week for more tips on our Tech Trick Tuesday posts. We will be finishing up with part 4 next week.

 

Brake Hose Service Ideas Part 2

Brake Hose Service Ideas Part 2

Just in case you missed part 1 of our Brake Hose Service Ideas from last week, we covered:

  • How to tell if a brake hose is still able to continue in service or not
  • What cracks mean on a brake hose and if it is serviceable when cracked
  • Is the pull on the vehicle from the brakes or from the brake hoses?
  • What to do with a caliper when servicing the vehicle
  • What heat does to brake hoses

Idea 7

This is the end result of what happens when too much heat reaches the crimped end portion of a flexible brake hose.

Brake Hose Service Idea 07

Idea 8

This is a comparison of a crimped hose end compared to one that has separated because of being heated with a torch.

Brake Hose Service Idea 08

Idea 9

This hose is an example of petroleum saturation and damage. It received, from a leak, a constant soaking of power steering fluid or some other lubricant and over time simply became soft and deteriorated.

Brake Hose Service Idea 09

Idea 10

Note the length of this hose and its position very close to the upper control arm. Putting the wrong hose on a vehicle or allowing a hose to slip in its mounting bracket by allowing a caliper to hang on it can cause interference issues between the hose and a suspension part or even the wheel.

Brake Hose Service Idea 10

Idea 11

Note the abrasion wear area of this hose. It was too long or mis-positioned and was rubbed against the tire/wheel during turns.

Brake Hose Service Idea 11

We will have more of ideas on brake hose service next week in our Tech Tricks Tuesday post.

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