brakes sticking -- any clues?

The brakes on my 2002 325cic sometimes fail to release. They apply light, increasing pressure until you can really feel it from within the vehicle. Rolling to a stop becomes impossible, the brakes grab and
even prevent me from rolling backwards on slight inclines. It's an intermittent issue -- one usually associated with warmer weather.
I'm stuck because my dealer (Dryer Reinbold in Indy) won't do anything unless they can re-create the issue. So unless it happens again while a)I'm close to their dealership, b) they're open, c) my mechanic is available, d) I don't have to stop and let them cool before getting there I'm hosed.
I did manage to get it there once while it was happening, got the mechanic in the car long enough for him to notice it -- but just for a second, as soon as he backed up and stopped they released. I understand the dealer won't fix what they can't clearly diagnose themselves -- but with winter approaching the car will be unsafe on snow or ice with the brakes as they are.
Any clues as to what could be causing them to fail to release properly? Recently I did have them replace the parking brake kit as it failed and had brake matter stuck in the brake caliper...
b
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Sounds like it might be a fault in the master cylinder. Seems unlikely, but if some crud (technical term) is intermitantly preventing the fluid returning through the m/c back into the reservoir, pressure could be building up in the brake lines. My first thaught would be to change the brake fluid, giving it a good flush though at the same time. If it is what I suspect, that would offer a reasonable chance of clearing the crud out of the system. Mike.
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snipped-for-privacy@gmail.com wrote:

Is there a chance that your car is equipped with a manual transmission and the "hill assist" (or whatever it is called by BMW) option?
If so, I wonder if it could be a malfunction of the system so that it thinks the car is rolling back so it applies the brakes?
If not, well... hmmm...
Cheers, Bob
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Nedavno snipped-for-privacy@gmail.com pise:
| The brakes on my 2002 325cic sometimes fail to release. They apply | light, increasing pressure until you can really feel it from within | the vehicle. Rolling to a stop becomes impossible, the brakes grab | and even prevent me from rolling backwards on slight inclines. It's | an intermittent issue -- one usually associated with warmer weather. | | Any clues as to what could be causing them to fail to release | properly? Recently I did have them replace the parking brake kit as | it failed and had brake matter stuck in the brake caliper...
Similar situation happened to me few years ago, only more drastic. After driving (Audi, not BMW) for an hour or so it was like I was trying to brake and accelerate at the same time. All four wheels (brake rotors) were (very) hot.
It turned up to be brake master cylinder. And it all started to happen after I went to a mechanic for some unrelated job, and he noticed that my brake fluid level was low (but it was only not at max), and added some. After that I had to change clutch hydraulic cylinder, and brake master cylinder. He must have added wrong brake fluid.
But this was a independent mechanic, not Audi dealer, BMW dealership should knew what is correct brake fluid for your car.
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Just passing through. :) This reminds me of a fairly similar fault I once came across on a UK made truck. It was caused by a faulty valve (air/vacuum) in the brake vacuum servo. Of course, I don't know if your vehicle uses such a brake servo (there are so many different ones used). It's often too easy to assume that the fault must be in the brake master cylinder.
Sylvain.

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snipped-for-privacy@gmail.com wrote:

Does it behave like the problem described here:- http://www.brakesint.co.uk/technical.html#techNote301
?
Andrew
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wrote:

That's a very good fault-finding guide. All you car drivers should _archive_ it.
Sylvain.

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All,
Thanks for the advice and ideas. The issue is now resolved. It took six visits to the shop, but they finally pulled and tested my calipers and found that the driver's-side rear caliper wasn't releasing properly. A new caliper and a brake fluid flush / fill / bleed has hopefully solved the problem.
The only lingering frustration is that the brake issue is why I took it in in the first place -- specifically the left rear brake. I understand the difficulty in resolving intermittent issues, but wish the dealer had taken the time to check the calipers on one of the first five visits to their shop...
b
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