Calipers wont release

Brakes for your Classic Mopar

  1. 74demon

    74demon Well-Known Member

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    Im sure this is a repeat issue but...here the deal

    70 swinger originally drum car now has 74 front brake wildwood rear brakes (got them dirt cheap new in box unopened will get matching front over winter) new rubber lines to calipers and rear axle new master cylinder new calipers pads rotors the fronts wont release unless i crack the line bolts at calipers ( bleeder made no difference) rears haven't had chance to look at that yet but im sure im not first guy with this issue of someone could point me in right direction i would appreciate it
     
    Last edited by a moderator: Aug 9, 2017
  2. MoparMike1974

    MoparMike1974 Well-Known Member

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    I would swap out the rubber hoses and see if that cures it. I have seen the rubber swell the line closed. I know your hoses are new but we all know the great quality of parts these days.
     
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    • 74demon

      74demon Well-Known Member

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      For got to mention the proportion valve is not new but never gave me a indication of any issues prior to this
       
    • RustyRatRod

      RustyRatRod 30 Degrees Outta Whack FABO Gold Member

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      Anything done to the master cylinder?
       
    • 74demon

      74demon Well-Known Member

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      Nope just a standard replacement part old one was leaking
       
    • plumkrazee70

      plumkrazee70 FABO Gold Member FABO Gold Member

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      Is it possible that you got a drum/drum master cylinder, which has residual valves in the ports? Im, pretty sure that was designed to keep pressure on the brake drum shoes.
       
    • RustyRatRod

      RustyRatRod 30 Degrees Outta Whack FABO Gold Member

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      Be CLEAR dammit. So then was it replaced when all this other was done?
       
    • 74demon

      74demon Well-Known Member

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      Yes it is possible i got one for drum car....once i got all my brake stuff to do the swap is when was replaced none of this has seen a street
       
    • plumkrazee70

      plumkrazee70 FABO Gold Member FABO Gold Member

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      Check the part no. That would be my guess though for calipers not releasing. Or possibly the slide bolts not greased up, but that seems like a reach.

      Check out Dr. Diff, he can set you up with the correct master.
       
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      • RustyRatRod

        RustyRatRod 30 Degrees Outta Whack FABO Gold Member

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        Unbolt the master cylinder and pull it forward. See if the calipers release. If they do, adjust the rod going into the booster shorter. Sometimes master cylinders are machined to different tolerances.
         
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        • 67Dart273

          67Dart273 FABO Gold Member FABO Gold Member

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          X2........or crack the line fitting with a rag(s) under and see if pressure releases
           
        • RedFish

          RedFish Well-Known Member

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          The brake lamp switch adjustment can hold the brakes on.
          It can also kill a battery in the opposite condition, so that adjustment should be checked with every master cylinder service.
           
        • G50

          G50 Tetanus

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          I was just scrolling along in here, searching for ideas. My front calipers were licking down and not releasing (all 4 brakes are all new). I popped the MC lose from the booster and BAM! everything's fine. bolted it back up and lock up :-( Come to find out (stupid me), brake pedal was returning enough to turn off the brake light switch but still engaging the MC. I hooked up a return spring and all problems fixed. I don't even know if my Dart Swinger was supposed to have a return spring. Anyone?

          G50
           
        • 72bluNblu

          72bluNblu FABO Gold Member FABO Gold Member

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          There definitely shouldn’t be a return spring on the brake pedal, something’s screwed up. If the brake pedal rod is too long it can do that. Or an internal issue with the master cylinder or the booster. But the brake pedal shouldn’t need any kind of a spring on it, that’s bad news.
           
        • RedFish

          RedFish Well-Known Member

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          Nope. No brake pedal return spring.
           
        • G50

          G50 Tetanus

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          OK So that explains why there was no return spring then. Now what? There's a contact bolt (if you will) between the MC and the BB. There's plenty of room to screw that in and lock it down again. Could it just be from run too far out from the factory (China?)?

          G50
           
        • RedFish

          RedFish Well-Known Member

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          maybe. Factory service manual will detail how that is supposed to be set up.
           
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