Not correctly “reading” brake pedals can lead to you wasting time. All too often, mechanics spend time trying to restore pedal height when no problem exists. Likewise, not learning how to read the brake pedal can lead to a vehicle delivery with a less-than-perfect pedal.
How to Read Brake Pedals
“Reading” brake pedals is the process of determining the height and feel of the brake pedals. In fact, pedal “reading” is an essential diagnostic step, and it is important to complete it correctly to perform an accurate diagnosis. As a result, you can return a customer’s car with a little extra confidence.
Brake Pedals - Height Adjustment
1. With the vehicle off, pump the brake pedal to deplete the vacuum in the
booster. As a result, the pedal should become very firm.
2. With your foot on the brake pedal and applying the same pressure as you would if you were usually starting a car, start the engine while noting the amount of pedal drop. If necessary, use a tape measure to accurately measure the amount of depth. For example, see Figure 40.1.
3. Figure 40.2 shows the same pedal with more pressure applying to it. Notice the pedal is now traveling 2.5” more. This measurement is typical and should not be considered a problem in the system on most vehicles.
4. When determining the condition of a brake pedal, check the pedal height with the vehicle in gear, and the brake applied just the point where it prevents the car from moving.
5. Next, test-drive the vehicle and make several stops applying light, moderate, and, if necessary, panic braking pedal forces.
NOTE: Never test drive a vehicle with an unsafe brake pedal.
6. Another good technique is to compare the brake pedal to another vehicle of the same make and model. It is essential to understand that there are wide variations on brake pedal feel and height between cars. Each car has to be assessed based on its characteristics and compared to similar vehicles.
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Well you covered vacuum boost brake pedal checking, how about hydrovacs and hydra boosters?? I deal with these on a regular basis. Their feel is often much different than a straight vacuum boost system. R, JOHN firstname.lastname@example.org