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Thread: Losing brake fluid

  1. #1
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    Default Losing brake fluid

    Ok guys - didn't drive the car for like 2 weeks, and it said brake fluid low. Topped it off. Drove about 300 miles. Brake fluid low. Where should I start?

    It's a 1992 525i. Any known problem areas?

  2. #2
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    grommets underneath the resouviour

  3. #3
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    Yeah, known problem areas. Obviously the first place are around the caliper hoses and connections. Then check the reservoir by the o-rings. These can begin to leak from age, from rough handling the reservoir, and from pressuring it too much while brake bleeding.
    Brandon J

  4. #4
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    any wet spots when its parked?

  5. #5
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    Quote Originally Posted by bahnstormer
    any wet spots when its parked?
    Yes. The car pisses oil (lifting head gasket from 15 psi of boost). Hm..


    Grommets eh? I don't notice and pressure loss when holding the brake when idling. I jam the pedal down hard and everything seems right - the pedal doesn't slowly leak down.

    I will check the grommets. Where exactly are they? Are they the things that the ETK shows the res sitting on between the res and the master cyl?

  6. #6
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    Quote Originally Posted by Jon K
    Yes.

    Grommets eh? I don't notice and pressure loss when holding the brake when idling. I jam the pedal down hard and everything seems right - the pedal doesn't slowly leak down.

    I will check the grommets. Where exactly are they? Are they the things that the ETK shows the res sitting on between the res and the master cyl?
    You won't loose pressure if those grommets are leaking, they are as you realized, the ones which holds the reservoir onto the master cylinder and not part of the pressurized braking system. They provide fluid which is gravity fed into they master cylinder.

    Incidentally, I pulled a brake booster with the master cylinder today out of an e34 535i and it was wet at that spot and along the boot at the firewall.
    BMW, THE ULTIMATE FLYING MACHINE

    SPEED AND POWER IS NOTHING WITHOUT CONTROL,
    THANK THE GERMANS, BMW HAS ALL 3

  7. #7
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    also maybe the pipe from the intake manifold to the brake booser is leaking. when i changed my headgasket the grommets were leaking then but since the car is running now it deosn't happen anymore. just a though.

  8. #8
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    Quote Originally Posted by Turbo Ready
    You won't loose pressure if those grommets are leaking, they are as you realized, the ones which holds the reservoir onto the master cylinder and not part of the pressurized braking system. They provide fluid which is gravity fed into they master cylinder.

    Incidentally, I pulled a brake booster with the master cylinder today out of an e34 535i and it was wet at that spot and along the boot at the firewall.
    I understandt hats not pressurized - thats why I think that could be it, though unsure. I can hold the pedal down and I don't feel it sink. Hmph. Do you think I can see the whole potential leaky area from above with a flash light?



    Kriss the connection from the intake manifold to the booster is a vacuum line. Nothing to do with the brake fluid really.

  9. #9
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    you probably want to pass your hand along the underside of the MC and see if it wet or if your hand ends up smelling like brake fluid. in that scenario, either the grommets (sp) are leaking, lines are leaking, or the mc is leaking from the seal. disappearance without accountability would be either a hard to find leak or a tear in the booster that allowed the fluid to be sucked into the engine from the mc.
    "..Torchinski v. Peterson that it is legal to carry a concealed weapon, so long the weapon is totally slick like a huge ass machine gun that you carry under a trench coat, like in the Matrix."


  10. #10
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    Quote Originally Posted by ryan roopnarine
    you probably want to pass your hand along the underside of the MC and see if it wet or if your hand ends up smelling like brake fluid. in that scenario, either the grommets (sp) are leaking, lines are leaking, or the mc is leaking from the seal. disappearance without accountability would be either a hard to find leak or a tear in the booster that allowed the fluid to be sucked into the engine from the mc.

    ^^^ It's the best method for checking for grommet leaks.

    What you can do as well is make up a brake fluid pressure rig to trouble shoot, it won't go to waste because you can use it for bleeding the brakes as well.

    Make a pressure rig using another reservoir cap and an external pneumatic pressure source, I am sure you know about this, pressurize to 5 psi and look for the leak.
    BMW, THE ULTIMATE FLYING MACHINE

    SPEED AND POWER IS NOTHING WITHOUT CONTROL,
    THANK THE GERMANS, BMW HAS ALL 3

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