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Help: Frozen Rear Brake Caliper? '87 245DL[ALL/1988] posted by Mr. Tool on
Thursday, 22 January 1998, at 4:12 p.m.
Hi: I'm doing a rear brake jobe on my 1987 245DL, 111,000. miles. Power Brakes. Question: 1. Should I be able to push (retract) the calipers (pistons) back in to make room for the new (thicker) pads. I have done this on brake jobs before, front and rear on Volvo's (240's)? 2. I can't budge the pistons at all. The other rear side (drivers) appears not to have a problem. 3. Are the pistons frozen? 3. Do I have to release some pressure on the brake fuild first? Never had to before. 4. Also, this rear side (passenger), the outer pad was completely gone, down to metal against metal. However, the inner pad and both pads on the other side had a lot of lining left. 5. Help. Any suggestions / ideas. thanks ..... mr. tool ...........
Brake Caliper R&R Notes[ALL/1988] posted by Dave Stevens on
Thursday, 22 January 1998, at 6:56 p.m.
Sounds like you've really got some sticky/frozen caliper pistons. You might be able to use a little brake fluid on the frozen pistons and eventually get them moving, but unless you can get them all working smoothly and evenly you will continue to have uneven pad wear and a tendency for brake drag to overheat and warp the rotors, not to mention the brake squeal.
You really need a complete caliper overhaul. The pistons need to be removed and cleaned. If the pistons are damaged or severely worn they will need replacing. New seals and dustcovers are then installed followed by a proper brake bleed. The proper procedure is to remove the calipers and service them on the bench using compressed air to force the pistons out. Easier said than done, though.
It is possible, but a bit tricky, to do it yourself. With the calipers unbolted away from the rotors, but still hanging on the brake line (careful not to kink and damage the brake line), clamp off each piston with a small c-clamp. Use brake pressure to push out one piston at a time until it just starts to weep then clamp it back in a little. Mark each piston for rotational alignment so that it can be re-installed in the same position (critical for some older Volvo brake systems if the piston face is machined at an angle). Careful, once one piston pops out you'll lose fluid and it will be game over. Generally a good idea is to start with the worst piston first. When all pistons are 99% out you can remove them by hand. Unless you own a mess of c-clamps, it will be best to r&r just one caliper at a time. Use brake fluid as lubricant on the new seals and pistons. The pistons can be pressed back in with c-clamps if you keep the pressure nice and square and are careful not to damage the new seals. For the brake bleed, you'll need a shop manual to figure out the proper bleeding sequence. Make sure you get every bit of air out or you'll have spongy brakes.
BTW. The brake pad metal-to-metal contact probably chewed your rotor up. Either get the rotor properly turned or get a clean one off a wreck. Check the archives for additional comments on rotor turning and caliper overhaul.
Re: Brake Caliper R&R Notes[ALL/1988] posted by Mr. Tool on
Friday, 23 January 1998, at 6:28 a.m.
Thanks Dave. I pretty much figured that was the way I was headed. I can purchase a rebuilt over the counter for $54. For $60. I can get one with new pads, pins and spring on it, ready to go. The only problem is those nasty rusted/frozen bleeder screws.......thanks again...... mr. tool ..
Re: Brake Caliper R&R Notes[ALL/1988] posted by Karl Koenig on
Saturday, 24 January 1998, at 11:14 p.m.
Dave's message really covers the job. I've popped out a frozen piston using the car's brake pressure--no problem.
And you always need to weigh the time/mess versus the cost of a rebuilt caliper. Maybe I'm getting old, I'd get the rebuilt.
Wish you well
Karl
86 245
81 BMW 528i
Re: Help: Frozen Rear Brake Caliper? '87 245DL[ALL/1988] posted by Ed Lipe on
Friday, 23 January 1998, at 8:41 a.m.
The piston could be out far enough to cock in the bore of the caliper...should be able to eyeball that one. If the piston is really cruddy (rust) then some heat may be necessary to extract it, then of course the caliper kit. Careful with that axe, Eugene...
Job Complete. '87 245DL[ALL/1988] posted by Mr. Tool on
Tuesday, 27 January 1998, at 6:59 a.m.
Hi, the job is complete, I went for the rebuilt caliper for $54. New AXXIS pads, cleaned up the stainless shims, and new pins, springs, and bleeder valves. Oh, yes, and a good dose of "anti-squeak" compound. thanks for the help........ mr. tool ..........