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Re: Stuck brake caliper piston. *Update* (archive)
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Posted by CFL on March 17, 2001 at 18:29:21:

In Reply to: Re: Stuck brake caliper piston. *Update* posted by george on March 17, 2001 at 16:47:39:


Ok, so releasing the bleeder valve didn't work, I ended up disconnecting the brake line and "sealing" it with plastic wrap and a rubber band to prevent it from leaking all the fluid out. With the caliper free, I removed the old cracked dust shield, sprayed the piston with WD-40, and gently hammered the piston back in.

I could reassemble everything and bleed the brakes, but would that be the proper way to do things? Where should I go from here?

(excessively curious and brave (read stupid) novice)

I don't have a good feeling about this George.
You should've lubed with brake fluid not WD-40.

What I would suggest at this point is not driving the car until this is properly fixed (no too difficult really).

You'll need a rear caliper rebuild kit and some new brake fluid. The rebuild kit is a new seal and a new dust boot. Also buy some really fine sandpaper like 1200 or 1600 grit, and a can of brake cleaner.

You'll want to remove that piston using the brake pedal again, or if you can remove the caliper and take it somewhere where it can be removed with compressed air.

I'm betting with the cracked boot some moisture got in there and you have a rusty spot on the caliper where the piston is getting hung up (right on the edge of the opening). Sand the rust away with the 1200/1600 grit sandpaper and brake clean often so you see how it's going.

After all that is nice and clean, use the new seal and dip it in brake fluid and position it inside the caliper bore. Now the tricky part, the dust boot, for that I'll point you to this site which has pictures.... go under e30 maintenance, then brakes, then rebuild.
http://www.neilwerke.com

I suggest you buy a large c-clamp like the one being used on that site, hammering was not a good idea, you may have damaged both the piston and the caliper bore. After you assemble everything, bleed that caliper and it wouldn't be a bad idea to bleed all the others.

Have a fun Sunday with the M and good luck!


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