Stuck front Calipers - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 08-14-2006, 02:08 AM   #1
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Default Stuck front Calipers

Just wondering.. how does the caliper work?? Wat controls how far and how it releases from the rotor?

How to diagnose the issue?? And minus the possible lack of grease on the slider pins.. how would I know I guess more importantly is when it'* time to replace the calipers or fixable?

I have a parts car.. and the caliper hasn't been used for quite a few months.. will it still be good with all the lack of use and rust? Or is it better to get new (rustless)?
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Old 08-14-2006, 04:25 AM   #2
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The caliper floats on pins that are lubricated with silicone grease and sealed with rubber bushings. These need to be clean and functioning to allow the caliper to apply and release properly. When you press the pedal, you force brake fluid to push out a piston in the caliper that sits behind the inboard brake pad. When the inboard pad contacts the rotor, the piston continues to push out in its bore causing the caliper assembly to slide inward on the pins until the outboard pad engages the rotor. This pinching action on both sides of the rotor is what slows the rotor and attached wheel. There is no return spring to move the pads away from the rotor, but, when the pedal is released, the pads tend to retract a little bit away from the rotor. The spinning and flexing of the rotor as you drive quickly moves the pads slightly away to provide clearance and free-wheeling when you release the brakes.

As the pads and rotor wear down, the piston must move farther out in the bore. But as disc brakes are self-adjusting, the only evidence of this will be a visual reduction of the pad and rotor thickness and the dropping level of fluid in the master cylinder reservoir as the space under the piston is taken up by brake fluid.

The piston and bore are protected by a rubber boot. If it is undamaged, and the piston is free to move in the bore, some external rust is not a problem.

One pad worn more than the other is a typical symptom of a caliper that cannot slide freely on its pins or a piston that tends to stick in its bore. A problem with older cars is internal deterioration of the flexible brake hose that attaches to the caliper. The internal rubber layers can delaminate and become jammed in the bore of the hose acting as a check valve, preventing the release of pressure behind the piston and causing the caliper to stick.

When you install new pads, open the bleeder screw on the caliper before you push the piston back home in its bore. That will flush the dirty contaminatied fluid from the caliper and prevent it from flowing back into the master cylinder and causing problems with the master cylinder bore and metering passages.

Bleed the brakes after installing the pads to flush out the old fluid and replace it with new.
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Old 08-14-2006, 01:24 PM   #3
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thanx.. I will look into it ASAP
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Old 08-14-2006, 01:26 PM   #4
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Hey bud... when you pull the pins and clean them.. lube with caliper goop. I use a high quality synthetic found at all autoparts stores. works wonders
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Old 08-14-2006, 01:53 PM   #5
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Thanx boost monkey.. time to go shopping again
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Old 08-14-2006, 01:56 PM   #6
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Sad part...is you can buy the little tube for like $3 or the monster bottle for $5...

Ps... Lash'll chime in soon...lol
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Old 08-14-2006, 01:56 PM   #7
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Quote:
Originally Posted by Drifter420
Thanx boost monkey.. time to go shopping again
Last time I changed disc brake pads, I got a small packet of the lube at the front desk for $0.99. There'* more than enough in there for one set of brakes, both sides.

IMO, unless you do it real often and am more organized than I am, those packets are a good way to get the specialty products.
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Old 08-14-2006, 02:27 PM   #8
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Nobody else mentioned this, but be sure you check out your brake lines as well, a collapsed brake line can cause a caliper to stick as well.

Your brake lines should be hard and you shouldnt be able to push in on them very much at all.

If they are soft and spongy they need replaced.
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Old 08-14-2006, 03:16 PM   #9
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Quote:
Originally Posted by LittleHoov
Nobody else mentioned this, but be sure you check out your brake lines as well, a collapsed brake line can cause a caliper to stick as well.

Your brake lines should be hard and you shouldnt be able to push in on them very much at all.

If they are soft and spongy they need replaced.
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Quote:
Originally Posted by bill buttermore
One pad worn more than the other is a typical symptom of a caliper that cannot slide freely on its pins or a piston that tends to stick in its bore. A problem with older cars is internal deterioration of the flexible brake hose that attaches to the caliper. The internal rubber layers can delaminate and become jammed in the bore of the hose acting as a check valve, preventing the release of pressure behind the piston and causing the caliper to stick. .
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Old 08-14-2006, 08:01 PM   #10
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So after I visually check for signs of missing boot rubber around the bore.. is there a way to check if it'* going back in correctly without having to re-install and monitor for lack of release again?
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