You need to do it in pairs. DO NOT split the caliper.
I know labor wise, installing a new caliper is easier. However, being short on cash made me go with the rebuilding route. Actually, you are not rebuilding, just resealing. The calipers were not leaking, but the dust shields were about non existant.
I took some pics as well. Pics are here:
Rear Brake Caliper rebuilding write up. - PeachParts Mercedes ShopForum
Tools needed:
Power drill and polishing flap wheel to polish the poston, if needed.
Air compressor w/blow gun (if you have them)
Two flat head screwdrivers
19mm 1/2in socket and ratchet
17mm 1/2in socket or proper wheel lug wrench
14mm flare wrench
11mm flare wrench
9 mm flare wrench
Large Channel lock pliers
Brake parts or carb cleaner
Shop rags or paper towels
3in wide x 9in x 1/8in thick piece of steel, or something else you can find. I used an old 9in edger blade.
Some sort of air block to use on the master cylinder. I used plastic wrap to act as a seal between the M/C cover and fill neck. That way you do not lose all the brake fluid.
Lovely and friendly assistant to help bleed the brakes. (My wife played this part. I'm lucky she is always willing to help)
Here is what I did:
1. Raise the car, support w/stands.
2. Remove the wheels.
3. Using the 11mm and 14 mm flare wrenckes disconnect the rubber line from the metal line. If you need to change pads and rotors, now is a good time.
4. Using the 19 mm socket, remove the caliper hold down bolts and the caliper.
5. Clean of the caliper as good as possible.
6. Use air gun to remove the pistons. Make sure you have rags in between them to avoid damage.
7. On mine, only one piston came out using the air. So I removed the dust seal from the one that stayed in the caliper, and then used the two flat head screwdrivers to pull the piston out. If you do not have access to air, use this method to remove the pistons.
8. Clean off the pistons and the cylinders. Mine were dirty. Luckily, no pitting or corrosion was present. If any is found, replacement calipers are in order.
9. Remove the old seal from inside each side cylinder. I used one of the flat head screwdrivers. Be careful not to score the inside of the cylinder.
10. Polish the pistons, if needed. Mine had some brown gunk adhered to them near the outer portion. I used the polishing flap wheel. (no sand paper only 3M polishing (like an SOS pad) and canvas.) It took that stuff right off without scoring the piston.
11. Insert the new piston seal in each cylinder. Use new, clean brake fluid to lube the seal.
12. Install the new dust shield on each piston. Note the orientation of the seal in relation to how it seats on the caliper.
13. Lube the pistons w/ brake fluid.
14. Insert one piston in to a cylinder. It is hard to press in. MAKE SURE THE MIDDLE LARGER "C" SHAPE IS FACING UP IN RELATION TO HOW THE INSTALLED CALIPER IS ON THE CAR.
15. Used the long wide flat piece of metal as a press. One hand on either side of the metal or caliper. It is your choice on how to do that. I used an old wood stove with the cover off as a platform to press the caliper and piston.
16. Repeat step 15 for the other piston.
17. Use the old dust shield as a helper to press the dust sheild to the caliper. Use the channel lock pliers to seat the dust seal.
18. Make sure all is seated well.
19. Install the caliper, install the brake pads, reconnect the brake lines.
20. Loosen the bleeding screw with the 9mm flare wrench.
20. Remove the air block from the M/C.
21. Wait for brake fluid to begin dripping out of the bleeder. Then tighten it.
22. Have lovely assistant press and release brake pedal, under your instruction while you loosen and tighten the bleeder, until all air is removed.
23. Refill Master cylinder.
24. Repeat steps 3-23 for remaining calipers.
