A broken brake piston is a common cause of disc brake malfunctions and should be immediately be taken care of, especially if the brakes are no longer functioning. And if you're planning on fixing a brake caliper piston by yourself, you need to do so at a slow and methodical pace to ensure that no mistakes are made during the process. So take your time and be sure to follow the steps below.
Difficulty level: Moderate
What you'll need:
- Piston repair kit
- Car floor jack
- Tire iron
- Ratchet set
Brake caliper piston removal tool/air hose
Step 1: With the car parked on a stable and level surface, engage the parking brake and raise the vehicle using a floor jack. Once it's lifted off the ground, place jack stands on your vehicle's designated jacking points and remove the jack.
Step 2: Remove the lug nuts with a ratchet or tire iron. You can also loosen them first before raising the wheel for added leverage, but make sure not to completely remove the nuts from the threads until the wheels are in the air. Once the nuts have been taken off, pull out the tire from the wheel hub and place it on the ground face up.
Step 3: Detach the brake pads from the caliper by removing the retaining clips. Use a vise grip to loosen the clips and slide out the pads.
Step 4: Have some press on the brake pedals, which will force the calipers to expose the brake pistons.
Step 5: Remove the piston from the brake caliper one at a time. You can use a special removal tool for this, although you can also use a pressurized air hose. For the latter, hold one piston with a C-clamp and blow out the other one using the hose. Wrap the caliper in rags to absorb any brake fluid sprayed out by the pressurized air.
Step 6: Clean out the inside of the caliper, the brake disc, and the brake pads. We also recommend putting an oil pan below the caliper and letting the escaping brake fluid drain into it.
Step 7: Inspect the piston for signs of damage and wear. Scrub off any dirt and rust and replace any worn cylinder seals, dust boots, and retainer pins. However, if the piston itself shows signs of cracks or fissures, it is no longer safe structurally and must be replaced completely.
Step 8: With the pistons cleaned and its seals and pins fixed or replaced, slide the pistons back into the caliper. Take note that the piston must be properly oriented with the rotor.
Step 9: Reattach the brake pads. The pistons need to be pushed into the brake rotors in order to slide the pads in, so either have someone step on the brake pedals again or compress the brake caliper with a C-clamp in order to slide the pads back into place.
Step 10: Return the tire to the wheel hub and secure it with the lug nuts. Lower the car gently into the ground.
Step 11: Refill the brake fluid reservoir and test your brakes. Take note especially of a spongy feel of the pedal; this means air has contaminated the brake pedal and must be bled out.