OT: Stumped by Pont Bonneville Brakes issue

Anonymous-0 · Dec 23, 2008

Hello, This is off topic, but there is such a great wealth of knowledge on here, I cant help but tap the well!

5 days ago, when backing out of garage, car didnt roll out easily..usually just put in reverse for 5 feet and it will roll out backwards. It didnt roll, after verifying no flat tire, I put in reverse again, had to accelerate to get to go out of garage. Rear brakes are engaging while in reverse without stepping on brake pedal.

The car will do this every morning, and also at other points in time, but almost always while backing up. After a few minutes of trying this, the brakes no longer stick. This car has 4 wheel disc brakes. Brake shop has checked it out and cant find any sticking calipers, etc. It didnt act up for them.

I also believe the rear brakes might be engaged while going forward, as it did this for about 300 feet the other day, then when released you could feel it and the car rolled better.

Any ideas? ABS problem? SHould I flush the fluid?

THanks in advance!

rrlund · Dec 23, 2008

Does that have a cable to the emergency brake? If so,could it be frozen and causing problems?

Roy in georgia · Dec 23, 2008

if it is both back brakes that is one thing but if you can tell if it is 1 side the break hose could be causing the problem. They deteriorate on the inside and cause a blockage.

Michael Soldan · Dec 23, 2008

The brake shop should have used lubricant on the sliders and the clips that hold the pad as well as on the retaining bolts. Calipers will seize up and require replacing. I have never encountered what you describe from faulty ABS. Faulty ABS usually lights up on your dashboard,will show a code, you brakes will continue to work only as regular brakes.

Allan in NE · Dec 23, 2008

Mark,

I left GM in '99 so take this with a grain, okay?

But, what you are describing sounds just like a plugged transmission filter. Sluggish reverse when first started cold and usually always will show up in the dead of winter.

Hope ya find the problem,

Allan

Roy in georgia · Dec 23, 2008

I looked at it as the brakes but this could be true

Anonymous-0 · Dec 23, 2008

I think id try to isolate it to a corner if I could, next time you feel it dragging, after it frees up stop the car, get out and feel the discs, one or more of them should be noticeably hotter than the others. Then at least youll know which corner (or end) to concentrate on. Then after that when it does it again you coast to a stop, put it in park( without touching the brakes ) and crack the bleeder on that wheel, if its under pressure youve got master cyl or divider valve problems if not youve got a stuck piston. If you find both discs hot on either front or rear Id go straight to the divider valve (think thats what they call it} just my thoughts....OCG

Anonymous-0 · Dec 23, 2008

If you think it might be tranny probs instead of brakes just let it warm up for a few mins before trying to move, should at least let you isolate the prob. which is always a good first step before ya start fixin...lol...OCG

Allan in NE · Dec 23, 2008

Or,

Back the car in the garage and try it in drive first thing in the morning.

Since reverse has a double gear reduction, it takes twice the oil and twice the line pressure to move the outfit backwards. That's why the problem always will show in R first.

Plus, sticking brake(s) won't usually "fix" themselves after warmed up. :>)

Allan

davpal · Dec 23, 2008

I think those cars probably have rear calipers that adjust by using your parking brake. In other words every time you apply the emergency brake the cable pulls on a mechanism like a ratchet and it threads the caliper inside its housing and tightens up the pads. I have them on the back of my car and they are a real rinky dink set up. I would take them both off and buy the KD tool that you need to thread the calipers back in. Its a square thing that goes on a 3/8 ratchet. Costs about ten bucks. Thread them back in, get some new pads if you need them and check to see that the brake cables are free. Its like a mechanical brake and a hydraulic brake combined. Good luck.

John - OH · Dec 23, 2008

Just a thought but it could be the emergency brake. Some GM's the emergency brakes built into the back of the rear rotors, like a small drum brake setup. Had similar situation on a 01 silverado, rust had caused the one shoe to come loose and for whatever reason would only drag in reverse and only some of the time. Just an idea.

relaurain · Dec 23, 2008

I have had this happen with the shoes sticking to the rotors.
You didn't say if they some loose all of a sudden or if it is a gradual release. If it is sudden, could be ice, if you are in the cold. If not a ice thing, buy better semi-metallic shoes and they won't stick!! Cheap organic shoes when they heat-up will stick like this.
Semi-metallics all the way around is the way to go!!

Brian Jasper co. Ia · Dec 24, 2008

Twice the oil and line pressure to move in reverse? Double gearing? No, that's not how it works. Line pressure is regulated by varying the displacement of the hydraulic pump as commanded by the PCM. Line pressure raises with torque request.(how far you push gas pedal) Forward or reverse, it's simply a matter of which combination of clutches are commanded on and off.
That said, check the parking brakes. Cold moist air can make brakes grabby. If the park brake is not fully released and is dragging a bit, it can do exactly what you're describing. The filter in a transmission is large enough to hold all of the friction material and not plug. If the trans filter were plugged, it would be slipping bad, fluid would be black.

OT: Stumped by Pont Bonneville Brakes issue

Anonymous-0

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rrlund

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Roy in georgia

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Michael Soldan

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Allan in NE

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Roy in georgia

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Anonymous-0

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Allan in NE

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John - OH

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