Intermittent brake overheating

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Old 06-13-06, 03:37 PM
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Intermittent brake overheating

My Saturn LS2 V6 2000 with ~90k miles on it developed intermittent/nonrepeatable brake failure caused by overheating of the right rear wheel - and only the right rear wheel. Now that I am sensitive to the symptoms, I can preempt the problem by responding to a slight softening of the pedal 'feel' or the high-pitched metallic whine that sometimes (but not always) presages the problem after about half to one hour of driving.

This car has 4 wheel disc brakes and when the problem occurs, both the front wheels are typically warm and the left rear wheel is cold to the touch as you would expect. The right rear wheel has waves of heat emanating from it and is too hot to touch. The problem is resolved by splashing water on the caliper/disc which instantly boils off making the car look as if it on fire (I have also had the problem resolve itself by pulling into a rest stop and driving back and forth a few times). A few miles down the road when I stop to check both rear wheels are back at the same temperature again. Usually the problem does not repeat for several weeks and I think it once went over 3 months without a recurrence (back when I wishfully thought that not using the parking brake at all might help - it didn't).

The sympathetic dealer has looked at the car and replaced various brake parts and insists that there is no problem, which there isn't except for the odd day of the month when I start to lose my brakes. The rest of the time everything works just fine. Since there is no way to replicate the problem except when I am on a highway miles away from any shop (or my driveway) I would really appreciate any suggestions as to what might be wrong. Everything I find on the net assumes the problem is constant, or that it applies equally to both front or rear wheels. Could it be just the one caliper even if the dealer has examined it? Is it even faintly possible that the section of the hydraulic line on only one side of the car is checking the fluid flow randomly??

Thank you for fielding this one...
 
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Old 06-13-06, 04:01 PM
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I can think of cars that have experienced this problem before. The problem is that it has been just about everything involved with the brakes.
I do not have intimate knowledge of this specific model so some of these items may not apply to you. Some brake problems only chow up in the situation you describe because the problem is causing just enough drag that over a long period of driving, it will build up enough heat to show up. Although the problem may be there all the time, with shorter drives it deos not seem to be a problem. The other thing with brakes getting hot is that once they start to get hot, everything expands and what was a slight drag, now becomes a major drag which in turn causes more heating and more drag. A vicious cycle.


Several things I would look for:

If the E-brake is a mechanical actuation of the caliper, check to be sure it is totally released. If it is applying a slight drag, it may cause problems as described above.

A brake hose can cause a slight resriction for the fluid causing drag. This one will often build on itself and become worse after long trips.

If it is a sliding caliper (as oppoised to a fixed one. a fixed one will have pistons on both sides of the caliper while a sliding caliper will have piston(s) on one side only), the slide hardware may be sticking. Sometimes a wear groove becomes a hang up point.

the caliper itself. What retracts the piston in a caliper is only the stretch of a square cut seal. It doesn't take too much gunk in a caliper bore to cause the piston to stick some.

The list can actually include almost any other part of the braking system but since it shows up on only one wheel, I would tend to discount the others at this point.

I have also seen a brake pad get caught in a wear groove in the carrier or get bound up because of rust build up in the groove where they ride making them tight.


I have had and seen a brake hose cause more elusive problems than just about anything else in the system. Most of the other problems are somewhat apparent to a mechanic but the hose gets overlooked or discounted often when it is the culprit.
 
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Old 06-13-06, 10:58 PM
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is the left rear tire breaking at all???
 
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Old 06-14-06, 12:50 AM
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hmmm..can't seem to figure out the real problem. Is it really the brakes or the wheels?
 
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