Paging brake experts

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  • robo_trigger
    Wrencher
    • Oct 2011
    • 210

    #1

    Paging brake experts

    Okay so I've been having some serious brake issues with my girls e30. It's an 87 325e auto. About two months ago the brakes crapped out on her (went to the floor). So I replaced the mc and did a full bleed (well almost, one of the rear bleeders sheared off so I couldn't get one of the rear calipers) but the pedal seemed good and all the other lines were spitting clear fluid so I let it be.

    1-2 weeks later, it craps out again. Now I should mention that the mc seemed to have a little fluid coming from somewhere, either the reservoir seals or the line fittings, I tightened up the line fittings more and that seemed to solve that problem. Thinking my issue was air in the lines from the unbleed rear I replaced the rear brakes with two reman ate units (beck arnley). Bleed it up good and it seemed to be road worthy again.

    Fast forward another couple of weeks, after driving two hours west to my hometown she tells me that the pedal went to the floor again, so she leaves the car and I have it sent to my old mechanic for a vacuum bleed thinkin air was in the system still after my manual bleed. He keeps it for a week, bleed it twice and gave it a clean bill of health. She goes out to get it, drives it 100 miles home and it's good for another two weeks. Now this morning the pedal went to the floor again.

    The replaced m/c was a NOS ate unit if that matters. Now im pretty stumped here, and I'm getting sick of throwing money at the problem, is it possible my master cylinder is slowing taking on air and that's what's causing the slow failure? It seems to come on without warning. The car is working fine and then one day she goes to start it and no brakes.

    Any ideas brake gurus?
  • jlevie
    R3V OG
    • Nov 2006
    • 13530

    #2
    Did you use a new, or rebuilt master cylinder? The low priced rebuilt units are a roll of the dice. Sometimes you get one and sometimes you don't.

    The pedal, after behaving normally, going to the floor is a leak in the system or a bad master cylinder. When you pull the master cylinder, always check for brake fluid in the booster. If there is brake fluid in the booster, replace it along with the master cylinder. Brake fluid will destroy the diaphragm is booster fairly quickly.
    The car makes it possible, but the driver makes it happen.
    Jim Levie, Huntsville, AL

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    • robo_trigger
      Wrencher
      • Oct 2011
      • 210

      #3
      But could a bad one be brought back so many times like this? It was a new Old stock ate model so maybe the seals were dry or something. The brakes will perform fine for weeks and then suddenly nothing.

      Comment

      • jlevie
        R3V OG
        • Nov 2006
        • 13530

        #4
        Aged seals could do that, or the unit could have just been bad.
        The car makes it possible, but the driver makes it happen.
        Jim Levie, Huntsville, AL

        Comment

        • robo_trigger
          Wrencher
          • Oct 2011
          • 210

          #5
          I just assumed if it was a bad unit the brakes wouldn't have firmed up like that. Oh well, time to order another m/c.

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          • Danny915
            Wrencher
            • Sep 2012
            • 200

            #6
            Get another m/c or even upgrade to an e36 m/c (great upgrade IMHO),check rubber brake lines on the caliper, and inspect reservoir for cracks. Also make sure to replace the O-ring when installing new m/c, very important. If problem persists I would monitor for leaks you may have a kink or pin hole allowing air in.

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            • robo_trigger
              Wrencher
              • Oct 2011
              • 210

              #7
              Replaced the m/c and booster with a used girling setup I had for an emergency. Seems to have firmed up. After a few days loosened up a little bit but brakes still engage as they should. Perhaps this was the problem? Funny you mention the o-ring, I have a distinct memory of replacing it but I don't think it was there when I pulled everything apart. Maybe that was the source of the problem?

              Time will only tell if the current setup holds up. Every other time it lasted about 2 weeks, but the brakes feel better this time around (probably a result of the notoriously firmer pedal feel from the girling setup).

              Comment

              • hopeful
                Advanced Member
                • Dec 2012
                • 113

                #8
                you dont have oil in the system do you?... when it goes to the floor, does pumping it rapidly bring it back to life?... any leaks anywhere? Pedal going to the floor sounds like a dead m/c, but even then pumping it up should make it okay if its fairly new... hmm weird, let us know what you find!

                edit: whoops missed your last post for some reason, carry on!

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