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E12 calipers are pretty easy to rebuild.
Read this FAQ completely well in advance of the job as there are things you can do a week in advance that will help the job go well.
Things you'll need before you start:
Chock the opposite wheels, e.g. if doing the front, chock the back, and vice versa. Lift the car and support it with stands. Never work under a car with a jack! Remove the wheels.
Remove the pins holding the brake pads in place with a Phillips screwdriver or punch. Also remove the anti-rattle spring clips that were held in by the pins. Note they may be missing.
Press the brake pedal about half way once or twice (It's not a good idea to push the brake pedal all the way to the floor - it can be harmful to the master cylinder seals). Do this with the engine off. Examine all pistons for travel. In ideal conditions, they will all reach the rotor. This will not happen unless you have maintained the brakes properly. In real life, some will move, others will be frozen.
The moving ones should be immobilized with the ½-inch blocks of wood. Depress the brake pedal half way again and check for travel of the remaining piston(s). As each one if freed, it should be immobilized with a wood block. When all the pistons are free you can remove the pistons. Grab the reduced diameter end of the pistons (the rusty cruddy part that is smaller than the rest of the pistion) gently with the Vise Grips and and rotate the pistons back and forth while easing the pistons out.
Two bolts hold each caliper in place. They should be loosened, and the brake lines removed from the calipers. After the lines are disconnected from the caliper, the mounting bolts should be removed completely.
Remove the calipers from the rotors. Do not split the calipers. The bolts can be used only once, and are no longer available.
The calipers will be dirty and the dust boots will be torn. Remove the mounting rings from the dust boots with a screw driver. Remove the dust boots and discard.
Great care should be exercised with the pistons. Scratching the sides will result in leaks. With pliers, grasp the TOP of the pistons and work them out completely. With a plastic toothpick or brass pick, remove the rings from the piston bores. These surfaces should also be treated with care to avoid scratching.
If you don't know when the rubber flex hose were replaced, you should replace them. Braided steel hoses will improve the feel of the brake pedal and look cool to boot. Pelican Parts has the best price I've seen to date on the rubber hoses. Either will be SO much better than the old clogged rubber hoses you're using now.
Soak the pistons and calipers in solvent - the longer the better. Rinse the parts with brake cleaner and allow them to dry. Remove rust, dirt, and mystery crud from the pistons and bores using brass or copper scrubbing pads (Chore Boy) and/or brass brush. Make sure what ever you use won't scratch steel. Test on a piece of scrap steel to be sure. A little brake fluid will help. Then soak all the parts in brake fluid.
Inspect the pistons and sealing areas of the calipers. Any rust or pitting is not good. Replacement pistons are available from Walloth & Nesch (see links area) and maybe your dealer. If the calipers are scratched badly or rusted, they should be replaced with rebuilt units.
Fit the rubber seal inside the bore, ensuring that it is flush with the walls and not rolled or twisted. Mount the rubber boot on the top of the piston, and insert it in the bore. It should be easy to push in with two fingers. Never force the piston into the bore. If you can't push it in with two fingers, it means that the piston is not straight in the bore.
Place the other end of the dust boot on the caliper and secure with one of the metal rings. Use care not to gouge the boot. Repeat this process until all pistons are replaced and all dust boot are installed.
Replace the calipers on their mountings, reconnect the brake lines, and bleed the brakes. Don't switch the calipers from side to side. Make sure that all the bleed fittings point up.
The fluid levels should never go below the minimum marker on the reservoir. If the level does drop below the minimum, air will be introduced and you'll have to start the bleeding process over.
Additional information and links:
Here's a link that will open in a new window to the Senior Six Registry E3 Caliper (which are pretty much the same as e12 calipers) Rebuilding FAQ by Bill Bowes: http://texasconsulate.com/faq/calipers.htm (opens in new window). The Senior Six Registry can be found at http://www.seniorsix.org
Also as the Ate E12 brake calipers are the same as some Ferrari calipers, here's a link (thanks to Peter Claassen) for FAQ of Ferrari Ate calipers http://www.r-design.net/308/techtip2.htm
*Ask me how I know
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