Brake piston repair can be undertaken on your own if you have a little mechanical knowledge and a do it yourself attitude. If your brakes are feeling a bit soft when you apply them, a number of things might be wrong. You could have air in the brake lines, the master cylinder could be leaking or an individual wheel cylinder might need repair. In addition, if your car uses a power brake booster or an electric brake booster, it might be malfunctioning as well. A brake bleeder can help you get the air out of the lines, but if you need to repair or replace a piston from a brake cylinder, here are the steps to follow.
Tools and Materials
- Ratchet or tire iron
- Car jack
- Brake caliper piston removal tool
- Air hose
- Drain pan
- Brake bleeding kit
- Piston kit
Step 1: Remove the Wheel and Raise the Car
With the ratchet or tire iron, loosen the lug nuts, raise the car with the jack and secure it with a jack stand, then remove the lug nuts and the tire, setting them aside.
Step 2: Remove Brake Pads and Caliper
Remove the retaining clips that hold the pads to the caliper and detach the pads from it. Compress the brakes so that the caliper pushes the brake pistons to the rotor. Now that the pressure is off of it you can remove the caliper.
Step 3: Remove the Pistons from the Caliper
You will need to keep one piston from moving while you remove the other. You can use a brake caliper piston removal tool, but it is a special part. After you secure one piston, you can also use a pressurized air hose to blow out the other piston. Use a small C-clamp to secure the one piston while you blow out the other. Wrap the caliper in a rag before you blow out the other piston to keep from spraying brake fluid everywhere.
Step 4: Clean Up / Replace
Now that the pistons are out, you can clean up the caliper. The piston kit contains a seal for the piston cylinder, a rubber dust boot and retainer pin to hold it in place, and replacement retainer clips to hold the pads to the caliper. These parts should be replaced. Chances are, the pistons themselves just need cleaning.
Step 5: Reattach Caliper
When every piece has been cleaned, put the pistons with the replaced parts back on the caliper. The pistons must be correctly oriented with respect to the rotor. There will be a cut out area on each piston that tells you the proper way of reassembly. When you make the final adjustment, apply the brake with the pads removed from the caliper so the pistons compress towards the rotor. Leave just enough room to put the pads on so you won't have spongy brakes.
This is a challenging job, but once you do it and get the hang of it, the next time will be easier. Make sure you bleed the brake cylinder after doing the replacement work, refilling the master cylinder after you do.