Brakes Caliper Dust Boot
Despite the fact that new or remanufactured calipers are inexpensive and usually available, there are a few good arguments to rebuilding the one you have. The parts to do the rebuild are very inexpensive; usually less than five dollars not counting the brake fluid. There is also the satisfaction of being able to do this yourself. As long as you follow a few safety precautions and know when rebuilding is not an option, this should be relatively easy.
When trying to rebuild a caliper, which includes replacing the dust boot, one literal sticking point will concern the bleeder valve on the caliper. If it's stuck, you're going to want to use a welding torch and heat this red before trying in earnest to remove it. If this part breaks off, your options are going to be trying to drill out and tap the hole, or replacing the caliper. If you've changed the brake fluid every couple of years, this should not be a problem. Moisture will work its way into the braking system, degrading seals and rusting out lines if this is not done, and will lead to seized bleeder valves. This is another story.
Raise the end of the vehicle being worked on and support it with jack-stands, after loosening the wheel nuts or bolts. Do not use the jack that came with the vehicle, or use any jack to support the car. I have had one fall down on me and nearly lost the fingers on my right hand when trying to take off the tire. The wheels will come off next and beneath that, there are your calipers; one on each wheel.
Remove the banjo bolt holding the brake line and insert a small rubber hose in the end of the line. Remove and discard the copper washers as these will leak and new ones are cheaper than a crash. There are usually two bolts that hold the caliper to the steering knuckle, but every one is different. Pay attention to the way it came off and use the other side as a reference when trying to get it back on again. The caliper will be filled with brake fluid, cover this with a rag get it away from the car. The fluid will eat the paint in short order. Clean up any spills with clean water.
Put the caliper on a solid surface, you will likely see one piston inside with a rubber dust boot. If there is more than one piston, better take this to get it exchanged. If you're going ahead, place a block of wood which is thick enough to cushion the piston and thin enough to allow it to come out. Do not use your fingers to catch the caliper, you will lose them. Use an air hose, and a little amount of pressure, to ease the piston out. You can usually wiggle it out the rest of the way by hand. Do not use tools to pull the piston as you will damage it.
One you have it out, use a non metal tool, such as a cuticle stick, to get the dust boot and seal out of the bore. Pay attention to where these go to make your life easier. Once these parts are out, clean the inside with denatured alcohol or brake cleaner. Do not use WD 40 or any other petroleum product, as you will ruin the replacement seals. Remove every bit of dirt from the inside and outside of the caliper. The main reason why these fail is that they aren't properly cleaned. Once cleaned, inspect the inside of the caliper bore and the piston. Minor scratches can be buffed out with crocus cloth, but the parts will need to be cleaned again. Deep scratches require replacement of the caliper. This will be likely if the dust boots are breached as they will let dirt in to ruin the seal. As long as you're satisfied the parts are absolutely clean, you can install a new seal and dust boot in the bore. Using your fingers and clean brake fluid as a lubricant, work the seal in its groove first, making sure it's flat inside and not twisted.
The dust boot goes on the piston, again, using clean brake fluid as a lubricant, slide the boot into the bottom of the piston. Use the bottom of the piston to seat the boot into its groove in the caliper. a twisting motion is called for. This is tricky and requires patience. Once it's seated, make sure the piston is perfectly square and not cocked inside the bore. Hand pressure will get it in, so you don't need to use a C clamp to muscle it in. Press it in and work the dust boot into the groove on the top of the piston. The rest is to reverse procedure to install. Use new washers on the banjo bolt, a small amount of anti-seize compound on the upper threads of the bleeder valve and bleed the brakes per manufacturer's directions.
When deciding whether to replace or rebuild a caliper, it's a question of time or money. Rebuilding takes more time and less money, replacing takes more money, and a lot less time. The condition of the parts and what you are comfortable with will determine whether or not to repair or replace.
