Brake System Tips | Master Cylinder Testing

Opening Seized Bleeder Screws

by Cade Thompson | Jun 2, 2021 | 101 Tech Tips, Brake System Tips

Every now and then, you might run into a stuck bleeder screw. This can be frustrating, especially because bleeder screws are supposed to be a simple step in the process.This article aims to help you know what to do whenever one gets stuck. Likewise, it goes over a few different solutions as each situation may differ.

Bleeder Screws Not Opening

The effort required to open bleeder screws will vary from on vehicle to another. The factors that effect this are:

Age of the vehicle
Operating environment
Rubber cap equipped
Whether they have ever been opened

Solution

NOTE: When attempting to open a bleeder screw always use a six point socket or wrench. Use of a 12 point socket or wrench will increase the chances for rounding the bleeder screw and increase the difficulty in removing it. Follow these steps to open the bleeder screw:

First, remove rubber dust cap if equipped. Using correct size wrench or socket, apply mild force to see if bleeder will open easily. If bleeder will not open stop attempting to open it without following the procedures below. Continuing to force it to open may result in breaking it

Bleeder Screws Method 1:

1. Use a hammer to tap on the head of the bleeder screw. Mushrooming the bleeder screw head is acceptable as long as the wrench or socket will still fit on (See Below).

2. Tap on the caliper housing all around the bleeder screw. After doing these steps try the bleeder again.

3. If necessary repeat steps 1 and 2 above. If bleeder still will not open you will have to use Method 2 listed below.

Method 2:

Using the tool shown in the image below and the appropriate size socket apply vibration to the bleeder screw while working the handle back and forth with even pressure. Do not force the bleeder screw. Keep applying the vibration until the bleeder screw opens. If the bleeder screw still will not open the caliper or wheel cylinder will have to be rebuilt or replaced

Any further trouble? Phoenix systems has developed an easy to use method that vibrates the bleeder screw while working it back and forth with a 3/4″ wrench. Click the button below for more information and a short video on how to use our BrakeFree product.

More Help

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GM W Body Rear Caliper Inspection Tips

by Cade Thompson | May 21, 2021 | 101 Tech Tips, Brake System Tips

Irregular pad wear, low brake pedals, and brake fluid leaks are all potential problems when it comes to front brake pad wear. This article will go over the causes and solutions to premature front pad wear and how to perform a caliper inspection.

Caliper Inspection Tips

The design of the caliper is such that it can suffer any number of failures. The symptom caused will depend on the type of failure. Here is a break-down:

Seized sliders – symptoms: irregular pad wear on rear, premature front pad wear and lack of stopping power and possibly low pedal
Lack of adjustment – symptoms: low brake pedal and premature front pad wear
Piston cup seal leaking – symptom: fluid leak seepage from piston vent and possibly friction contamination from brake fluid

Solution

A thorough inspection of the rear dis calipers will determine if they are functioning as designed. Follow the steps below:

1. When possible, apply the parking brake and check if either of the rear wheels will rotate. When one or more parking brake cables prevent this from being done, use a pair of channel locks to apply each caliper’s parking brake. In the case of either rotor being able to rotate with the parking brake applied then self adjustment has not been taking place. If both parking brakes are working properly go to step 3. If not, proceed to next step.

2. One or both wheels spin with parking brake applied – if the parking brake system works pump parking brake several times while holding the release lever. This should self adjust the rear calipers. If parking brake system is not functioning, apply and release each caliper’s parking brake lever several times using a pair of channel locks. Recheck parking brake function. If parking brake now holds the wheels go to next step. If one or both wheels still rotate with parking brake applied caliper replacement is necessary. It is advisable to replace calipers in pairs.

3. Parking brake holds properly. Remove calipers and check slide pins for free movement. If any of the slide pins are seized calipers should be replaced (See Figure 36.1). If any of the slide pins are sticking slider service should be performed or the option of caliper replacement offered to the customer. When all the pins move freely they should be lubed as part of the service. Go to next step.

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Effective Slider Service – Fighting the Elements

by Cade Thompson | May 20, 2021 | 101 Tech Tips, Brake System Tips

When moisture finds its way into a caliper housing, corrosion begins to cause premature pad wear. This article goes over the process of performing an effective slider service in order to fix the issue. Below, you will find pictures along with a step by step guide to complete the process correctly.

Before the Slider Service

Often times, calipers like the one below are given a quick glance and dubbed to be in good condition. In other words, if the dust boot is in one piece and the slider spin moves, then everything is ok. However, this is not the case. In truth, the caliper pictured below could have a number of conditions that would require a service. In addition to inspecting the part, it is important to consider other conditions that might have caused the vehicle to come back prematurely. In this example, the following results were found upon closer inspection:

Slider Pins

As pictured in image 35.2, one of the slider pins had a portion of the anodized coating worn off. (For those that don’t know, the anodized coating is important because it prevents corrosion.) As a result, the worn portion is now susceptible to corroding. In this case, industry accepted guidelines suggest that the pin should be replaced.

On the other hand, image 35.3 had not only lost it’s anodized coating, but had already begun to corrode as well. Much like a healthy pin, this part still moved as normal.

Caliper Housings

Floating caliper housings utilize casting holes to house the rubber bushings, o-rings or boots. In fact, Moisture intrusion into the caliper housing casting holes results in corrosion in many types of floating calipers.Likewise, as the casting holes corrode the inner diameter of the casting hole is reduced which leads to the rubber bushing, o-ring or boot to be squeezed around the mounting pin. This squeezing results in the caliper housing’s movement being restricted.

Now that we know the conditions that can occur because of moisture intrusion lets discuss how to prevent it or at least slow it down. First, a good dust boot does not mean moisture can‘t effect the pins as shown in Figures 34.2 & 34.3. Both of the dust boots on these pins were intact. Likewise the corroding of the caliper housing where the slider parts reside can‘t be stopped with a good dust boot. The key to preventing these types of problems is in forming moisture barriers. Follow the steps below to form moisture barriers on floating calipers:

Slider Service Steps

1. First, remove all caliper hardware from housing.

2. Second, clean the caliper casting housing holes. When flaking rust has formed tools such as a ball stone hone, wire brush or wheel cylinder hone will not be effective in removing this type of rust. Flaky rust such as that shown in Figure 34.4 will have to be either ground out using a dremel tool or blasted out using an abrasive blaster. The cleaning process should remove the rust but not good material. The end result should look similar to Figure 34.6

3. Third, use a high quality silicone lubricant to place a film in each casting hole as shown in Figure 34.7.

Adding Silicone

4. Coat the portion of the rubber boot that seats against the casting hole with silicone. Using the brush place a light coat of silicone on the inside of the rubber boot making sure to lube the sealing ridges on each end of the boot. See Figures 34.8 & 35.9.

5. Install the rubber boots into each of the casting holes. The silicone on the casting hole should mix with the silicone on the boot to form a protective layer as shown in Figure 35.10. Note: More is not better. Too much lube can cause more problems than it cures. The silicone in the casting hole combines with the silicone on the rubber boot to form an effective moisture barrier.

6. Place a layer of silicone lubricant on the sealing ridge of each pin as shown in Figure 34.11.

7. Install each pin in its rubber boot. The silicone on the sealing lip of the boot will mix with the silicone on the sealing ridge of the pin to form a protective layer (See Figure 35.12)

The steps above cover the process when servicing boot style floating calipers. The steps would be similar when servicing bushing and o-ring style calipers.

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Caliper Replacement Guidelines

by Cade Thompson | May 19, 2021 | 101 Tech Tips, Brake System Tips

There are so many variables that effect the operation of a caliper, it is impossible to place a generic lifespan on them. Because of this, a good mechanic will develop the ability to be able to accurately determine when it is time to replace the calipers. For your example, this article will go over the signs of wear as well as the different options of calipers out there.

Determining Caliper Replacement

Replacing calipers with every brake job would be considered overselling by most customers and regulators. On the other hand, never replacing calipers would be considered underselling by most shops. Typically, there are two groups of customers who should be offered the option of replacing the calipers. To emphasize, notice the word “option”, meaning the customer will have a choice.

Group 1: If the vehicle fits the following criteria the customer should be offered the option of replacing the calipers:

• The vehicle has high mileage
• Original equipment calipers are still installed
• Each set of pads lasts less than the previous set (premature pad wear)

Presenting Caliper Options

When presenting the option of replacing the calipers you should make the following points:

• First, explain to the customer that based on the vehicle’s history and current condition the only way to restore maximum pad life is to service the inside of the caliper. This usually means replacement. As a result, the function of the square cut seal will be restored. (See more info below for a better explanation of the square cut seal).

Group 2: When a vehicle fits the following criteria, the customer should be offered the option of replacing the calipers:

• Start by informing the customer that parts or labor will be required to restore the caliper’s. However, If the caliper requires the replacement of smaller parts, the customer should also be given the option of replacing the caliper (See Figures 34.1). Often times it can actually end up being more expensive to fix the caliper than to replace it.

Note: Without a proper inspection most of the conditions listed above would NOT be found.

More Info: Floating Caliper Operation

Calipers are not “instant on, instant off” parts. This is because they go through a cycle or process during both the “apply” and “release” phases. (See Figure 34.3).

Unapplied

Understanding these 2 processes is key to being able to identify many of the causes of premature pad wear. To begin, the “apply-cycle” starts with the application of the brake pedal, which results in pressure being generated in the hydraulic system. Likewise, hydraulic pressure created in the caliper housing pushes in all directions. In fact, the operation of the caliper works on the principle that things will take the path of least resistance. The easiest thing to move in a floating caliper should be the piston. Hydraulic pressure pushes the caliper piston into the inboard brake pad causing it to press against the inner friction surface of the rotor (See Figure 34.4).

Inboard Pad

Once the inboard pad is against the rotor, the caliper piston is no longer the easiest thing to move and system, causing pressure increase. Next, the easiest thing to move is the caliper housing. As a result, pressure acts against the caliper housing using the caliper piston as a backstop. This pressure causes the caliper housing to move toward the center of the vehicle on its mounting pins. Inward movement of the caliper housing pulls the outboard pad against the outer friction surface of the rotor (See Figure 34.5). Once both the inboard and outboard brake pads are against the rotor’s friction surfaces, increasing the hydraulic pressure results in even clamping of both brake pads.

Release Cycle

A different process takes place to allow the brake pads to release. For example, the part responsible for the release of the brake pads is the square cut seal. The square cut seal is a square o-ring that sits in a machined groove in the caliper housing. You’ll notices that the groove in the caliper housing is beveled towards the open end of the bore. This square cut seal forms a seal between the caliper housing and the piston’s sealing surface (See Figure 34.6).

As the caliper piston moves out to apply, the square cut seal is flexed into the beveled portion of the housing groove. Next, the square cut seal will remain in the stretched position as long as the brake pedal is applied (See Figure 34.7).

Finally, once the brake pedal is released and system pressure goes to zero, the square cut seal returns to its natural relaxed state because of its elastic properties. As the square cut seal returns to its natural state it pulls the caliper piston back with it. The relaxing of the square cut seal is what is responsible for the release of the disc brake pads.

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Wheel Tightening Procedures

by Cade Thompson | May 18, 2021 | 101 Tech Tips, Brake System Tips

When a wheel is installed incorrectly it can cause disc thickness variation in the rotors. As a result, the vehicle starts to experience pulses when braking. In contrast, when wheels are tightened correctly, the vehicle should maintain its proper condition. In order to prevent reoccurring pulsation complaints, this article will show you the correct procedure for installing and tightening wheels.

Installing a Wheel

The process of installing a wheel is very simple and only involves two key steps. When both steps are done properly whell induced runout will be elinated as a potential problem. For example, the steps are listed below:

1. First, tighten the wheel using the correct sequence. (More on that below)

2. Second, use a process called “step torquing”.

Wheel Tightening Procedures

By tightening the wheels lugs in the correct fashion promotes both safety and proper brake operation. In order to preform the installation correctly, all wheels should be tightened and torqued in the same process:

1. Hand tighten all lug nuts using a star pattern.

2. Next, tighten all lug nuts to approximately 1/2 specification using the same star pattern.

3. Tighten all lug nuts to full specification using the star pattern.

Note: If the wheel is not a 5 lug nut wheel, then use the proper tightening pattern listed in the image below.

Image Source: PROwheels

Note: When working on alloy or aluminum wheels we strongly advise re-torquing the wheels after a short test drive.

Note: Never use lubricants or penetrating fluids on wheel studs, nuts or moving surfaces. Likewise, wheel nuts, studs and mounting surfaces should be clean and dry. If penetrating fluid is used to remove the wheel lugs, clean the studs and nuts before reinstalling. If desired, a thin layer of moly-lube may be used on the inner mating surface of the rotor where it meets the hub to slow down corrosion.

Calibrating Your Impact Wrench

WARNING: Wear safety goggles when using torque sockets

Torque socket are calibrated to an impact of 250 lb.ft. with 90-100 psi of air inlet pressure. Because most impact wrenches vary from 100 lb.ft. to 600 lb.ft. with various air inlet pressures, it is necessary to perform a simple calibration in order to ensure that torque accuracy will be uniform with each respective socket. The steps below will go over how to calibrate the impact wrench:

1. First, tighten a wheel nut whith a torque socket. (For example, try 100 lbft. socket)

2. Second, test the torque setting of the wheel nut with a calibrated torque wrench (Preferably a dial indicator), by measuring the break away torque in the tightening direction.

3. If the torque of this wheel nut is more than 100 lb.ft., turn the impact wrench output down.

4. Repeat the above procedure until the wheel nut, torqued socket, and torque wrench are in sync. – Plus or minut 5 ft.lb of the 100 ft.lb. torque socket. As a result, the impact wrench is now calibrated for any of the torque sockets.

5. Each time the torque sockets are used, remember to set the impact wrench to the proper setting.

As long as the air inlet pressure is not changed, this setting will always be accurate for the torque sockets.

TIP: Failure to properly torque the wheels can take an otherwise perfect brake job and cause it to comeback with a reoccurring pulsation complaint.

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Hub Removal on Late Model Honda Trapped Rotors

by Cade Thompson | May 14, 2021 | 101 Tech Tips, Brake System Tips

Working on hub removal for late model Honda’s can become slightly more difficult than other hub removals. This is because it is not uncommon for this particular hub to become stuck, or “trapped”. This article will go over what causes these hubs to stick, as well as how to remove them. The process for this particular hub removal is not very difficult and, by using a simple trick, becomes fairly straightforward and easy.

Cause and Solution

As can often happen, these hubs sometimes experience rust and corrosion between the hub assembly and the steering knuckle. As a result, and with time, this corrosion begins to bond the two parts together. Effectively, the parts become rusted together as well as more difficult to separate. To fix the problem, the knuckle and hub must be separated from one another.

Hub Removal

1. Remove the knuckle assembly from the vehicle (Note that while this step can be skipped, we strongly advise removing the knuckle.)

2. Remove the four (4) OE hub retaining bolts. (Figure 32.1)

3. Install the four (4) 10×1.25mm x 3″ bolts, making sure to thread them in 1/2″ as shown in figure 32.2

4. Finally, using a hammer, drive the hub out of the knuckle using the heads of the longer bolts as drivers. Use an “X” pattern when doing this. As a result, this process will “walk” the hub out of the knuckle. (See figure 32.3)

More Mechanical Help

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Opening Seized Bleeder Screws

Bleeder Screws Not Opening

Solution

Bleeder Screws Method 1:

Method 2:

More Help

GM W Body Rear Caliper Inspection Tips

Caliper Inspection Tips

Solution

More Mechanical Help

Effective Slider Service – Fighting the Elements

Before the Slider Service

Slider Pins

Caliper Housings

Slider Service Steps

Adding Silicone

More Mechanic Help

Caliper Replacement Guidelines

Determining Caliper Replacement

Presenting Caliper Options

More Info: Floating Caliper Operation

Unapplied

Inboard Pad

Release Cycle

More Mechanical Help

Wheel Tightening Procedures

Installing a Wheel

Wheel Tightening Procedures

Calibrating Your Impact Wrench

More Mechanical Help

Hub Removal on Late Model Honda Trapped Rotors

Cause and Solution

Hub Removal

More Mechanical Help

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