W124 Caliper Repair Kit - Success!
Well, as per the previous thread, I purchased the W124 rear brake caliper "repair kit". The kit consisted of two pairs of rubber seals, one for each piston of the caliper (in the Fastlane picture, these are the four rings shown in the picture), thus four seals per caliper. I installed the seals over the weekend and am happy to report that this is an easy DIY'er project. It does not require you to disassemble the caliper. It took me 1.5 hours total.
In my case, the pistons on the calipers were fine - they were not seized or stuck. The outer rubber seals however had degraded and ripped, exposing the pistons. I thought I would post the technique below in case anyone else is doing this/thinking about it and has questions.
REAR BRAKE CALIPER SEAL REPAIR TECHNIQUE - (at your own risk, etc, blah, blah)
I removed the rear wheel and with the caliper still mounted, I removed the brake pads. I then removed the caliper and set it on top of a milk crate, still attached to the brake hose. The piston seals consist of two parts - there is an inner rubber ring and the main seal itself. The inner rubber ring sits inside the main seal and you install them together. The main seal has a steel ring INSIDE its outer perimeter for rigidity. You can't see it in the new seals (covered in rubber), but if your old seals were as toast as mine, you can see it rusting through them.
I inspected the pistons carefully and mine were in excellent condition - no rust/pitting. They both moved freely within the caliper, no binding. If I had detected any binding or physical damage, I would have opted for a rebuilt caliper at that point.
Removal of the old seal is easy. It just pries off gently with a screwdriver. Once off, I cleaned the area thoroughly with brake cleaner fluid and compressed air, ensuring that any loose rust/scale was removed. You mave have to extend your piston a bit to get the seal off - this will be apparent when you're working on it. I installed the seals one piston at a time. I did the inner one first.
Using a C-clamp, I held the outer piston in place. Then I gently pressed the brakes until the inner piston stuck out about 0.5 cm or so. The trick here is that you need to expose enough of the piston to seat the new seal to the piston itself. The seal has an outer ring (with the steel band inside) that seats on the outside of the piston assembly. There is an inner seal that goes around the piston itself. I sealed the piston first. Once the inner seal is on, you can gently press the outer seal into place. There is an inner ring seal (as mentioned earlier) that sits inside the main seal. This should be properly aligned when you are doing this. How it all fits together will be obvious when you are doing the job - I wish I had pictures...
To fully seat the new seal, which simply presses into place, I placed the brake pad against the piston with some thin cardboard around it to protect it. I then used another C-clamp to fully compress the piston into the caliper. Doing so presses the new seal into place neatly. Presto, that's it you're done! Do the same thing on the outer piston.
Like I said, it only took me 1.5 hours to do both seals on both rear calipers. I tested their function and they work perfectly. Onyl $45 and my rear calipers are as good as new!! I saved a bundle instead of buying rebuilt calipers. These things are pretty damn solid! I drove into work this morning and the brakes are solid and smooth! This forum rocks!!
Please feel free to ask any questions.
2007 E550 4Matic - 61,000 Km - Iridium Silver, black leather, Sport package, Premium 2 package
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1998 E430 - sold
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