Brake caliper not releasing on '92 Olds 88

Tiny
THEBURRUS1
  • MEMBER
  • 1992 OLDSMOBILE DELTA 88
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 291,000 MILES
On my '92 Olds Eighty Eight, the front right brake caliper does not want to release when you let off the brake pedal. This is now the 2nd refurbished caliber in two months Ive put on the car after the last obviously did the same as it it wore down the new pad in less than a month to metal on metal. All brake lines do not leak, master cylinder shows no signs of leakage. What if anything is left to might cause this? Any valves anywhere that are made to release the caliper after you take your foot off brake? I have no ABS and no traction control either on the car in case you need to know that. Thanks.
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Thursday, July 7th, 2011 AT 2:23 AM

5 Replies

Tiny
CARADIODOC
  • EXPERT
Does that brake drag while driving or is your diagnosis based solely on the rapid pad wear on one side?
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Thursday, July 7th, 2011 AT 2:36 AM
Tiny
THEBURRUS1
  • MEMBER
Yes, the brake drags while driving!
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Thursday, July 7th, 2011 AT 2:39 AM
Tiny
DANLESABRE
  • MEMBER
Have you tried bleeding all 4 wheels? (While ensuring there is always fluid in the master cylinder at all times)
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Thursday, July 7th, 2011 AT 5:44 AM
Tiny
CARADIODOC
  • EXPERT
The most likely cause is a sticking caliper on the right side but first of all, GM doesn't have much caliper trouble, and especially you aren't going to run into three of them. There are some other potential causes. When you get it to lock up again, park on a slight incline, (not a big hill, because I don't want to hear you had to chase after your car!), Shift it into neutral, then crawl underneath and open the right front bleeder screw. If the brake does not release, your new caliper is sticking. Since it's unlikely three pistons in three calipers would do that, I'd look closer at how the caliper is mounted. The mounting surfaces and slide bolts must be free of rust and pits and they must not be bent. All sliding surfaces should be coated with high-temperature brake grease, but even if they were not, you still shouldn't be having this problem.

If the brake DOES release at the bleeder screw, next time loosen the steel line at the master cylinder. If it does not release, suspect the rubber flex hose. There is a metal bracket crimped around the center of that hose. If rust builds up inside that crimp, it will constrict the hose. You'll be able to force fluid to the wheel by pushing the brake pedal but that fluid won't flow back when you release it. Use a large flat blade screwdriver to pry that crimp open a little to relax the hose. The additional clues are the brake pedal should feel higher and harder than normal.

If the brake does release when you crack the line open at the master cylinder, brake fluid is being trapped and can't get back into the master cylinder and reservoir.

GM has an oddball valve in the master cylinder that trips if the brakes aren't bled properly or if one of the two hydraulic circuits pops a leak. Since this is a "split-diagonal" system, that valve will block fluid flow to one front wheel and the opposite rear wheel. You will almost never notice a brake pull when that valve is tripped but the classic symptom is the pads on one front brake wear out real fast and the other side looks like new. You have a different symptom though in a brake dragging. That tripped valve doesn't cause dragging brakes.

Getting back to where the fluid is getting trapped, if the brake releases when you crack the steel line open at the master cylinder, suspect the brake fluid is contaminated with petroleum product. Sorry I can't tell you which line to loosen so you might have to try both of them. Proof of fluid contamination will be found by inspecting the rubber bladder seal under the reservoir cap. If it is ballooned up and mushy, you got junk. All of the rubber parts in the brake hydraulic system that come in contact with brake fluid are compatible only with glycol products. In petroleum products, they will grow and get soft. The lip seals in the master cylinder will grow past the return ports and block them. Eventually that will cause the left caliper to drag too. Lets hope it doesn't come to that. The fix for contaminated fluid is to replace every part with rubber parts that contact the fluid, flush and dry all of the steel lines, and refill the system with fresh, clean brake fluid. That means replacing the calipers, wheel cylinders, master cylinder, and all four rubber hoses. If any part is not replaced, the contamination will leach out of it into the new brake fluid and the problems will start all over.
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Thursday, July 7th, 2011 AT 8:19 AM
Tiny
THEBURRUS1
  • MEMBER
Okay, that all makes sense to me so I will take that into serious consideration. Thank you for taking the time to pass that along. I will post back if that or a couple other possibilities I look into don't work. Again, thanks!
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Thursday, July 7th, 2011 AT 9:07 AM

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