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Thread: 1984 318i E30 rear brake problem

  1. #1
    Join Date
    May 2023
    Location
    Sicklerville nj
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    7
    My Cars
    1984 318i bmw

    1984 318i E30 rear brake problem

    So originally when I got the car the pedal has always been soft but the brakes would engage. Then the driver side wheel cylinder was leaking fluid so I ordered two new wheel cylinders and put both in for the rear. Right after that the pedal came back pumped it up and it was hard as a rock. I bleed all for wheels made sure no air in the system. About a week later I was driving and as I hit the pedal it went down and stopped like usual but if I pushed it a little more it would go straight to the floor again. Did it a few more times now my pedals soft again and the back brakes stopped engaging we tried seeing if there was a problem with the cylinders and we put new lines coming from the cylinders to the rest of the lines. We tried bleeding them multiple times and they would gravity bleed perfect and when we pressed the pedal to bleed them it would coke shooting straight fluid out. I havenít leaked any fluid since and the pedal still soft but the front brakes still stop the car. I was thinking itís possibly the master cylinder or the brake booster but donít know wanna throw parts at it if thatís not the case.

  2. #2
    Join Date
    Mar 2020
    Location
    New Hampshire
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    38
    My Cars
    2013 328; 1984 318i
    What is your pedal feel without the engine running?

  3. #3
    Join Date
    May 2023
    Location
    Sicklerville nj
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    7
    My Cars
    1984 318i bmw
    Quote Originally Posted by Sunnyledge View Post
    What is your pedal feel without the engine running?
    Without a little tougher still can go to the floor but still doesnít get hard

  4. #4
    Join Date
    Mar 2020
    Location
    New Hampshire
    Posts
    38
    My Cars
    2013 328; 1984 318i
    I would think you need to replace or rebuild your master cylinder. A pedal slowly going to the floor, without a visible leak, points to the master cylinder.

  5. #5
    Join Date
    Sep 2007
    Location
    Regina, Sask, Canada
    Posts
    1,913
    My Cars
    82 320i 89 325i
    Quote Originally Posted by Sunnyledge View Post
    I would think you need to replace or rebuild your master cylinder. A pedal slowly going to the floor, without a visible leak, points to the master cylinder.

    it does sound like the mc

  6. #6
    Join Date
    Nov 2019
    Location
    Milwaukee, WI
    Posts
    513
    My Cars
    1989 325ix, 2003 4.4 x5
    I've always been told when you bleed the brakes, don't go all the way to the floor. This may push the piston in the MC past it's normal travel to an area of the cylinder which may be slightly abrasive, causing the piston to seal poorly. I'm not sure how true this is, but makes sense.

    - - - Updated - - -

    It's possible the MC was damaged while bleeding the brakes after the cylinder change or maybe it just went bad on its own.

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