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  1. #1
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    Help please: Sticking brakes!! Advice needed

    Hi, I wonder if anyone could help me please. I have an ‘87 e28 and I am having trouble with the brakes sticking. This seems to happen sporadically and I am finding it difficult to pin point the source of the problem.

    The seals on the callipers seem OK and the front seals have recently been replaced. I also suspect if it were a sticking calliper, it would stick more or less constantly. I have been unable to find whether the problem is at a particular corner: there is no excessive brake dust or overheating (the rear discs/rotors are set quite far back also, so heat would take a while to propagate forwards).

    Occasionally when driving, the brakes will bind so badly that it seems about 50% of the vehicles power has been taken away! However they will suddenly un-bind and the car feels fine! - very strange! I did wonder if it might be the handbrake mechanism, although things looked OK when I recently replaced the rotors and the linings didn’t seem too worn. Also, it seems to have little relevance to operation of the handbrake – I may try not using the handbrake, but the sticking still occurs. The car does not pull at all to one side either.

    Could it be the master cylinder? Or loose rubber or debris in a brake hose? The car has always been very reliable and although I can excuse the car this one problem, the problem itself is infuriating as it is so irregular! I would appreciate anyone’s suggestions and input from experiences. I can imagine a master cylinder is costly – I don’t mind this so much, but I would hate to fit one only for the problem to still occur! I could do with some help with diagnosis and troubleshooting!

    Many thanks to everyone in advance! Philip


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    Re: Help please: Sticking brakes!! Advice needed

    One thing you did not mention is what causes the situation to occur. Does it occur completely by itself or is it occasionally when the brake pedal has been pressed. I assume it's the latter. The typical causes of sticking brakes is sticking of the cylinder in the caliper bore. Typical failure of master cylinders is either leaks or the inability to pressurize the system. In other words you have to pump the brakes. It is possible that the lines themselves are acting as a one way check valve, but that generally only slows and not stops the release.

    Here are some questions. How long has it been since the hydraulics have been flushed? Was a DOT4 fluid used? Are we talking about an M20 (528e) or M30 (535i) powered vehicle?

    My best guess is a sticky caliper. even if the seal is good on the outside, moisture may have entered the system leading to corrosion on the inside. You might simply try flushing the brake system with a quality DOT4 fluid. If it's a manual, don't forget to flush the clutch hydraulics too.


    -----------------------------------------------------
    Richard O.
    1986 528e
    1989 325iX
    1998 328iC

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    phil_c
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    Re: Help please: Sticking brakes!! Advice needed

    I had a similar problem with the brakes. The best fix is to just replace the whole caliper (both sides of course) If the hoses are old it's good insurance to change them at the same time.

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    Re: Help please: Sticking brakes!! Advice needed

    Hello. Thanks for the help so far. The problem happens occasionally after braking, although it isn't immediately obvious and then the problem either remedies after a couple miles or if the car is standing for a while. And then may not occur again for a while - strange. I did wonder whether it was the handbrake, and I did try avoiding using it on a couple trips - but this wasn't conclusive!

    I think perhaps I'll strip the rear callipers and inspect the rear pistons. I changed the brake fluid about 2 years ago (probably due a change?) although this has been happening on and off for a year now! I know it may be a loose flap of rubber or similar a brake line acting as a one way valve. Perhaps I'll replace the hoses too.

    Any further advice would be much appreciated.

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    CLINTA74
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    Have you checked the emergancy brakes?


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    had this same problem awhile back....

    on the M6 .... I could drive it and would be fine, drive it again, it would be fine when starting out, then I could sit at a stop light on a hill, take my foot off the brake and it would sit there and not move.. start out and you could feel it drag, drive on the freeway and use the brakes, and then feel them drag and release until I used them the next time...

    Sound Familiar???

    Anyway, after chasing calipers etc.. in the end I changed the Master Cyl and guess what... they work like new again ... good luck... jsJohn Stein
    85 745 @ 1.2 bar
    85 M635CSi
    84 633

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    Re: Help please: Sticking brakes!! Advice needed

    Sorry to dig this one up, but I could do with some more help please! Thanks for the advice all that time ago!

    I have still been having on/off problems with the brakes sticking. Yesterday I did about 10 miles, and the car suddenly began sticking when I got home. Luckily I'd been working on the car earlier, and as such had my trolley jack out and waiting! I quickly jacked up the car on all four corners (one after the other!) and guess what?! ALL four wheels were stuck fully! They would barely move!

    As I've stated before, I have had sticking callipers in the past but this to me (as I've suspected) is a system-wide issue, rather than a single calliper. I have a feeling it may be the master cylinder (as JH Stein kindly suggested). Would other people agree that this is the most likely problem? What else could it be? Indeed the symptoms sound very similar to those that JH Stein mentioned previously.

    Thanks, Philip

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    Re: Help please: Sticking brakes!! Advice needed

    Hi Philip,

    I had the same symptoms I replaced all the calipers and still the problem persisted.

    Change the Master cylinder and you will fix the issue.

    1988 535IS 155K

    Peter

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    Re: Help please: Sticking brakes!! Advice needed

    Master cyl. the most likely, but the partitioning valve could also be plugged.

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    If you had the proper size wrench with you.

    You could have unloosend the brake lines at the master and seen if that made a difference. If it did then your master cylindr is indeed the culprit. For all four wheels to be stuck usually means that the master cylinder piston is not returning to its normal position. What really gets me is that you have had this problem for almost a year now and have yet to fix it.

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