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Brake Fluid Leak ?

Discussion in 'E30 (1984-1993)' started by Zdaneman, Jul 20, 2010.

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    Zdaneman

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    Since I'm not new to E-30 maintenance and trouble shooting issues, this one has me really scratching my head.

    A few weeks ago the brake fluid light started flashing. I checked fluid level which was a little low and added more brake fluid. Light went off. I started checking for drips and found a drop a two over a three or four day period. I had to go to Swedish German Auto later in the week to have the Air Conditioning serviced. I had them put it up on the rack and check for leaks. They reported there were no signs of a leak or any fluid trails on the under carriage. Mr Dye is pretty squared away mechanic and said lets watch it as see what happens. His only guess was either clutch slave cylinder or clutch master cylinder is going bad.

    Well about 5 days later, light starts to come on again, checked fluid again, a little low (between min /max). I added more fluid and took it to Ft. Belvoir and put it on the rack myself. I took a flashlight and a trouble light and spent 30 minutes looking for a leak. Nothing! I even lowered the car and pumped the brakes and worked the clutch several minutes trying to get it to leak. Still no sign of a leak anywhere.

    Anyone had this problem before? My only course of action is to replace both cylinders (master and slave) and see what happens.

    Its not leaking on the wheels either, checked all four. Any info would be great.


    Zdaneman sends
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    granthr

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    Where were these drips coming from? I would say watch this area. Place a clean piece of paper or something in that area so you can see fresh drops. A slave or master cylinder can fail internally, but they can only consume so much fluid before it starts to leak out.
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    John in VA

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    Have you looked for fluid inside of the car? Remove the panel under the steering wheel and look for fluid on it, on the carpet, or in the pedal box.
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    MGarrison

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    Haven't had your issue, but I'd think one of the hardest places to spot a leak would be where the clutch master comes through the firewall; I'm speculating the carpet could soak up some drips without showing much evidence otherwise. I'd think you could feel wetness or a residue on the cylinder, though. I could see a leak being difficult to spot around the brake pressure regulator (5), and at the rear, the 'distribution piece' (3) and the brake lines/junctions across the trailing arms. I suppose the clutch slave could leak at the piston seal, seems like that would become evident.

    http://www.realoem.com/bmw/showparts.do?model=1113&mospid=47309&btnr=34_0153&hg=34&fg=15

    Replacing the master & slave cylinders aren't your _only_ recourse; you could replace... everything else! But, I doubt anyone would expect that would be necessary. If you think you could be getting a trace drip, paper on the garage floor sounds like a good idea to me. At least it's probably unlikely to go away, more likely to get worse with time. Good luck figuring it out!
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    az3579

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    I've had a really weird time where I've gone through 3 master cylinders and still had leaking brake fluid. Turns out my brake booster or some kind of seal was defective; it was letting fluid in. Took out a good Gatorade bottle's worth of brake fluid before we realized that it wasn't right. Oddly enough, the booster worked fine with all that fluid in there.

    I know it requires disassembling, but there's no other way to check. If you come up completely stumped, I would check this.
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    MGarrison

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    The only way fluid could get into the vacuum booster would be from a bad master cylinder seal, ya? If it took 3 new master cylinders, that would either be a fluke, or indicate something about the vacuum booster function was damaging the master cyl. seals?
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    az3579

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    Precisely.
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    Zdaneman

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    Thanks

    I'll remove the dash under pannel this weekend, but I've not noticed any fluid on the carpet or mats? The leak seems to be coming from under the engine bay area. My brother had the same issue with one of his many Fiero's. His final solution was to replace both slave cylinder and clutch master cylinder, it worked.

    I'm not one to just slap on parts trying to fix something, so I'll keep looking. I'll take a look at the vaccume booster too!

    Thanks again all!

    Zdaneman sends
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    CRKrieger

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    Well, with such a small system, there are only three parts plus the connecting lines you can throw at it. Replace the slave. They all eventually fail anyway and they're the cheapest and easiest part to swap. At the same time, carefully inspect the lines to see if that's the source of your leak. If not, some further diagnosis is needed to decide whether it's the master (unlikely if it's entirely inside, as it is on the E28) or the booster.

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