91 Lumina rear brake caliper won't adjust

[Pablisimo]

Taking advice from various threads on this forum I've managed to finally replace the rear rotors on my 91 lumina and get the caliper piston cranked back in. Now the driver's side caliper won't adjust. Pumping the E-brake several times adjusts the passenger side fine, but watching the driver's side while a helper pumps the e-brake, I see the piston rotate out and then slide back in when the brake is released.

Two oddities occured when doing this side. First the piston head on the right side has a small seal in the center while this side does not have that seal -- there's a hole where the seal should be. Second, I had a fierce time getting the parking brake tang back on and while fiddling with it at one point brake fluid leaked out the back side of the caliper where the tang attaches.

I've spent way too much time on this "little job" and need to get done. Do I need to replace the missing seal? Rebuild the caliper? Punt and buy a new caliper?

A side question is if I end up having to take this off again, is there a recommended way to get the spring and brake cable back on?

[maxwedge]

Get another caliper they were troublesome from day one.

[Blue Bowtie]

Not to pile on, but Max is correct. For people who don't routinely use the park brake, these calipers are problematic. The park brake actuator screw needs to be cleaned and lubricated with clean brake fluid. The lip seal must be in place.

I usually advise people to throw away the little square tool which is used to screw the piston back onto the actuator, and instead ratchet the actuator while pushing the piston straight back in. This will either free the actuator or reveal a stuck one.

http://www.automotiveforums.com/vbul....php?p=5878362

I had numerous sets of these on several Fieros I owned, and they all worked just fine if they were maintained and used. I also have them on my old TA, and they work just fine, too. The best thing you can do is keep them clean and use the park brake regularly (as in every time you park).

[Pablisimo]

The parking brake has been used regularly at least the last 3 years. The actuator and piston moved freely right from the start. The piston just doesn't stay in place. I wonder if I didn't get the lip seal properly positioned. As long as I'm taking it apart, that'll be an easy check.
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The seal was indeed the problem, it apparently wasn't seated properly. Reseating it and ensuring the actuator screw was fully extended results in a fully working caliper. Making sure the parking brake was loose at the equalizer made attaching the cable and spring easier but still not as straight-forward as I would expect. Thanks guys.

[dannym]

Originally Posted by Pablisimo

The parking brake has been used regularly at least the last 3 years. The actuator and piston moved freely right from the start. The piston just doesn't stay in place. I wonder if I didn't get the lip seal properly positioned. As long as I'm taking it apart, that'll be an easy check.
-----
The seal was indeed the problem, it apparently wasn't seated properly. Reseating it and ensuring the actuator screw was fully extended results in a fully working caliper. Making sure the parking brake was loose at the equalizer made attaching the cable and spring easier but still not as straight-forward as I would expect. Thanks guys.

Those rear brake calipers were the subject of a class action lawsuit because of their high failure rate. I got only a few dollars because I had done the work myself! I have found that the caliper piston does not seize, but the sleeves around the mounting bolts do. I tried the parking brake application routine, but the problem came back. Each time a brake job is done, I remove the rubber sleeves, and clean off the old grease, replace the grease only with special high temperature disc brake grease, so it doesn't melt and run onto the friction surface, or dry up. Permatex makes a nice green colored synthetic one. Also, you can replace the sleeves and rubber seals. If the caliper no longer "floats", eg slides in and out by hand on the mounting bolts, then the sleeves are frozen. JC Whitney used to sell an anodized set, maybe no longer available, but Advance Auto still sells replacement sleeves. Look at their online catalog. The only other alternative is to replace the calipers periodically. When the sleeves freeze, since the piston is still working, you will see that the pad on the inside, where the piston is, will be worn. but the outside pad will not be worn, since the caliper no longer floats and no longer applies pressure on the ouside pad against the rotor. If the piston won't screw in (retract), I have found that when the piston won't screw in, opening the bleeder valve on the caliper while pressing the piston in with a brake pad spreader tool on the old pad (easier than a C clamp), takes the pressure off the piston, makes it easy to screw it in with a cup type tool attached to a socket handle and extension, much better than the cube type, more pressure can be applied. The brake spreader tool applied to the old pad also prevents damage to the little plastic valve in the center of the piston. Buy one with a pressed in nut for a sufficient amount of thread to apply pressure without damaging the threads. The cheap ones only thread the plate. Lisle makes a nice one. The piston must be turned in, especially with new rotors, or there will not be sufficient space between the pads to clear the rotor when reinstalling the caliper. Disconnecting the emergency brake cable is not necessary once the pressure is released, and the piston is screwed in.

[manicmechanix]

Those calipers are a nightmare to work on and their sliding sleeves do get locked up. I think when you are removing them, you are suppose to release the tension at the parking brake equalizer, and instead of trying to turn the piston in take the rear parking brake lever off and run the piston in with a C-clamp with the brake pad still on to protect the plastic check valve and to square the piston in. I think trying to turn them in screws them up. They don't work like the Japanese calipers.

[Pablisimo]

Originally Posted by manicmechanix

I think when you are removing them, you are suppose to release the tension at the parking brake equalizer, and instead of trying to turn the piston in take the rear parking brake lever off and run the piston in with a C-clamp...

Yes, you definitely need to release the tension at the parking brake equalizer and remove the brake cable. Not doing that was one of my many mistakes that complicated the job.

These pistons do need to be turned in. There are several techniques recommended on the forum for doing this. I ended up using the Auto Zone "Borrow a tool" program which got me the mechanic's grade tool on loan for a refundable deposit. Cranks the piston back in seconds.

[Schurkey]

Originally Posted by Pablisimo

Yes, you definitely need to release the tension at the parking brake equalizer and remove the brake cable. Not doing that was one of my many mistakes that complicated the job.

These pistons do need to be turned in. There are several techniques recommended on the forum for doing this. I ended up using the Auto Zone "Borrow a tool" program which got me the mechanic's grade tool on loan for a refundable deposit. Cranks the piston back in seconds.

I must be doing it wrong, then.

I unscrew ONE nut on each caliper; pull off ONE washer on each caliper along with the park brake lever.

Then I push the piston back in with a C-clamp vice grip. The park brake screw spins instead of the piston, while the piston slides straight into the bore. Once the piston is back in the bore, I just re-attach the park brake cable, lever, washer, and nut. It could not be simpler, faster, or easier.

I think rear-caliper problems on the W-body is an over-rated concern.

I've got two Luminas; a '92 and a '93. The '92 was purchased in November, '92; the '93 I've only had for about three years. The '92 now has ~115K; the '93 has ~140K. I have had exactly Z-E-R-O problems with rear calipers other than routine pad changes. What I have had problems with are power boosters--I could use BOTH FEET on the brake pedal and push for all I was worth--and the cars would not stop hard enough to activate the anti-lock.

Replacing boosters on both cars with standard, ordinary rebuilt units made a WORLD of difference.

[manicmechanix]

Originally Posted by Schurkey

I must be doing it wrong, then.

I unscrew ONE nut on each caliper; pull off ONE washer on each caliper along with the park brake lever.

Then I push the piston back in with a C-clamp vice grip. The park brake screw spins instead of the piston, while the piston slides straight into the bore. Once the piston is back in the bore, I just re-attach the park brake cable, lever, washer, and nut. It could not be simpler, faster, or easier.

You're doing it right. The ones turning the piston in are doing it the wrong way. Like I said, you're not suppose to turn the piston in like a you would on a japanese caliper. You're suppose to take the parking brake lever off and push the piston in with a C-clamp.

I think rear-caliper problems on the W-body is an over-rated concern.

I've got two Luminas; a '92 and a '93. The '92 was purchased in November, '92; the '93 I've only had for about three years. The '92 now has ~115K; the '93 has ~140K. I have had exactly Z-E-R-O problems with rear calipers other than routine pad changes.

I agree that rear caliper design doesn't have as many problems as most people say, but one problem they have that isn't over-rated is the caliper slides freezing up.

They are a pain to change pads on especially if you don't know how to do it though. You have to release the parking break tension, remove the parking braking lever, then push the piston in, then reinstall everything and readjust the parking break. That a lot of steps just to replace pads. there might be shortcuts like unboltening the rear parking breaking lever while it's still attache, but I'm not sure. A lot of other rear-calipers all you have to do is screw the piston in, and most new designs they separate the parking break from the caliper piston and all you have to do is press the piston in.