Need some help with Brake issues

Brakes for your Classic Mopar

  1. RustyRatRod

    RustyRatRod I was born on a Monday. Not last Monday. FABO Gold Member

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    • C2ndLTpigeon

      C2ndLTpigeon Mopar or no Car! FABO Gold Member

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      Here is a video of the issue, first burp pushing pedal down, once its bottomed releasing causes the 2nd burp. No air in the system.
       
    • C2ndLTpigeon

      C2ndLTpigeon Mopar or no Car! FABO Gold Member

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      Anyone know what the issue was with the master or what might be causing it to do that?

      I sent the master back today, ordered one from Classic Ind, along with a Combination valve.
       
    • RustyRatRod

      RustyRatRod I was born on a Monday. Not last Monday. FABO Gold Member

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      That's normal.
       
    • C2ndLTpigeon

      C2ndLTpigeon Mopar or no Car! FABO Gold Member

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      Something had to be causing the fluid to go low in the front to higher in the back reservoir, that cant be normal.
       
    • RustyRatRod

      RustyRatRod I was born on a Monday. Not last Monday. FABO Gold Member

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      Ok.
       
    • Dana67Dart

      Dana67Dart The parts you don't add don't cause you no trouble FABO Gold Member

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      The 2 cylinders are internally tied together via passages. If the pistons are at the wrong places they could pump fluid from one resivour to the other.
       
    • C2ndLTpigeon

      C2ndLTpigeon Mopar or no Car! FABO Gold Member

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      Changed the master with a new one today same issue but not as fast. I bought a new combination valve but tried the master first. Not sure what else it could be? This is the same master cylinder that is on my buddies 75 duster with power brakes and his works fine.
      20210922_174907.jpg
       
    • inertia

      inertia Well-Known Member

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      Leak in the rear .
      Air in the front .
      jmo.
       
    • Demonx2

      Demonx2 FABO Gold Member FABO Gold Member

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      Did you ever solve your issue? If so, how? Inquiring minds want to know!!
       
    • C2ndLTpigeon

      C2ndLTpigeon Mopar or no Car! FABO Gold Member

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      Yes I did!
      Ended up being the proportioning valve. I purchased a new one from classic industries. When I got it I disassembled it to make sure it had no burrs and give it a clean. I then pulled the old one off and it had markings like it was rebuilt. Took it apart and most of the internal valves and sprigs were gone! and on top of that it was filthy. So this was the reason it was not functioning correctly. Kinda surprised it my brakes even functioned for the year I drove the car.
       
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      • Demonx2

        Demonx2 FABO Gold Member FABO Gold Member

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        Interesting! I'm in the middle of doing all new brakes/lines/etc on my car hence why I asked. I'm not changing the prop valve...but maybe I should. We'll see. My pedal goes too low before it gets firm so I've got an adjustable pushrod coming for it. We'll see if that helps anything. It's an original 4-piston K-H power disc up front w/ 10" x 1-3/4" rear drums but the power booster is removed. Putting new rear wheel cyl's on it - trying to decide if I should stay with the 15/16" bore like original or drop down to the 13/16" like some people suggest to reduce the propensity to lock up the rears. It has a new 1-1/32" master cyl on it.
         
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        • C2ndLTpigeon

          C2ndLTpigeon Mopar or no Car! FABO Gold Member

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          Sure was, but I learned something new. At minimum I would take yours apart, very simple design. Clean and inspect it.
          Good luck with your project!
           
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