If you’re comfortable working on cars, then rebuilding brake calipers isn’t an especially big job. It’s something you should do every other time you replace your brake pads. Rebuilding the brake calipers will ensure they don’t seize up or freeze on you, which could be extremely dangerous when you’re driving.
Step 1 - Preparation
The simplest thing to do when you’re going to rebuild your brake calipers is to purchase a brake caliper rebuild kit from an auto parts store. Make sure it’s the right one for your vehicle. It’s not an expensive item, and contains most of the things you need for the job.
Slightly loosen the nuts on the front wheels and then jack up the car. Make sure the vehicle is in park, with the handbrake on, and that there are chucks behind the rear wheels. Place jack-stands under frame for safety. Loosen the wheel bolts completely and remove the wheels to expose the brake calipers. Put layers of paper under the car to catch any drips of brake fluid.
Step 2 - Brake Caliper Removal
How you’ll remove the brake calipers will depend on the make and model of your vehicle, so you’ll need to follow the instructions in your service and repair manual. Be careful when you remove the caliper from the mountl, as you don’t want to twist the brake line. With the caliper removed, detach the brake line and put a vacuum cap on it. Cap the hole where the brake line enters the caliper to keep out dust and dirt.
Step 3 - Removing the Piston
In order to remove the piston, first you’ll need to take off the dust boot so you can access the piston. Once you’ve done that, take a small piece of wood, at least ½ inch thick, and place it so it’s between the caliper and the piston. Hook up a compressed air gun to the brake line hole on the caliper and slowly shoot air in. The piston will eject onto the wood. Make sure your hands are clear of this.
Step 4 - Cleaning the Piston
To clean the piston, wipe it carefully with one of the rags. Now you need to check the piston and clean it thoroughly. Use a scrub pad on it until it’s shining, at which stage you’ll be able to see any rust or pitting. If you find some, you’ll need to replace the piston.
Step 5 - Piston Seal
The next thing to do is replace the piston seal that is in the cylinder of the brake calipers. Using your fingernails, pick it out, then clean the cylinder with a rag that’s been heavily soaked with brake fluid. Allow to dry, after which you should coat a new seal with brake fluid and put it in place.
Step 6 - Replacing
Now, push the piston into the cylinder until it’s about hallways in. Put a fresh dust shield on the piston. Using a compression tool, force the piston all the way back into the cylinder. Once you’ve managed that, replace the dust boot on the caliper, stretching it so it fits neatly in the groove. Now you’ve rebuilt your brake calipers and you can reassemble them.