How to Diagnose Sticking Brake Calipers
- 1). Start the vehicle and place it in gear or drive on a flat surface. Release the clutch slowly for a standard transmission, or release the brake pedal for an automatic transmission. If the vehicle rolls slowly, apply the brake hard. Let the vehicle move slowly forward again. If it feels like it's sluggish or does not move at all after the brakes have been applied hard, this could indicate sticking calipers.
- 2). Test drive the vehicle. Apply the brakes in a low-traffic area while holding the steering wheel firmly. Apply the brakes a few times. This will heat the brakes up on the wheel with the faulty caliper piston, which will aid in the diagnosis.
- 3). Park the vehicle on a flat surface. Place a hand near each tire without touching the rim. If one rim has intense heat coming from it after the test drive, this might be the wheel with the faulty caliper.
- 4). Place a wheel chock against the outside tread of a tire on the opposite axle from the brake caliper being diagnosed.
- 5). Loosen the lug nuts on the vehicle a full turn with the lug nut wrench.
- 6). Hoist the quarter of the vehicle with the jack and support it onto a jack stand.
- 7). Check the temperature of the rim and lug nuts before attempting to fully remove the lug nuts. If necessary, allow time for them to cool before proceeding. Remove the lug nuts when ready, then remove the wheel.
- 8). Check the temperature of the caliper with your hand before attempting to touch it. If necessary, allow time for the caliper to cool before proceeding.
- 9). Remove the caliper bolts with a wrench or ratchet and suitable socket. Alternatively, you can try to compress the caliper first using a C-clamp. This should be done on front calipers only. Rear caliper pistons on many models require a caliper piston tool kit.
If the piston of the front caliper compresses, then the caliper piston is good. Try to move the caliper back and forth by hand to determine if the slides (or slide bolts) are sticking. If the piston compressed, but there is no movement in the caliper, the slides or slide bolts need to be removed, cleaned and lubricated. - 10
Pry the caliper off of the integral knuckle with a pry bar. Some calipers have pads attached to the housing, while others will leave the pads behind on the knuckle. Hang the caliper to a suspension component to avoid letting it hang from its hydraulic hose.
For pads left on the knuckles, check the pads for movement across the integral knuckle, where the backing plates of the pads contact the knuckle. Often, pads can become dry from heat and exposure and begin to stick on the knuckles, which might give off a false symptom of a sticking caliper. - 11
Compress the piston for the rear caliper, or if the front caliper piston could not be compressed as illustrated in Step 8. For rear screw-in pistons, use the tool kit to turn the piston clockwise. If the piston turns very difficultly or not at all, the piston is stuck and the caliper needs to be replaced.
Source...