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David_krystof's avatar
David_krystof
Explorer
Dec 31, 2016

76 Dodge Sportsman Class C, Brake Issues, wont hold pressure

I have a 1976 Dodge Sportsman Class C Motor home. I have replaced ALL NEW the master cylinder, power booster, front calipers, rear wheel cylinders, pads and shoes. I have bench bleed the master cylinder, bleed the brake lines and also reversed bleed. It took all the fluid it needed to fill up the master cylinder from the wheels but still can't keep pressure on the break. It pumps up but won't hold the pressure.
Class C
  • Fulltimers's avatar
    Fulltimers
    Explorer
    Dec 31, 2016
    donn0128 wrote:
    Bad master cylinder if there are no leaks.


    I agree. Fluid is passing by the plunger.
  • BTPO1's avatar
    BTPO1
    Explorer
    Dec 31, 2016
    I agree that the master cylinder could be bad even if new. It could also be a soft rubber hose that is expanding but not enough to burst. I have seen this on older brake hoses. It could either the front sides or the rear. JMO
  • K_Charles's avatar
    K_Charles
    Explorer
    Dec 31, 2016
    If there is no external leak, the master cylinder is the the only thing it can be.
  • David_krystof's avatar
    David_krystof
    Explorer
    Dec 31, 2016
    Brand new master cylinder. It took all fluid needed to fill MC from the wheels but the pressure just doesn't hold.
  • gbopp's avatar
    gbopp
    Explorer
    Dec 31, 2016
    David_krystof wrote:
    Brand new master cylinder. It took all fluid needed to fill MC from the wheels but the pressure just doesn't hold.

    A new master cylinder can be bad.
  • David_krystof's avatar
    David_krystof
    Explorer
    Dec 31, 2016
    This is second master cylinder I've tried brand new not manufactured. I moved cylinder from power booster and there was no fluid leaking past back into the booster.
  • cmeade's avatar
    cmeade
    Explorer
    Dec 31, 2016
    BTPO1 wrote:
    I agree that the master cylinder could be bad even if new. It could also be a soft rubber hose that is expanding but not enough to burst. I have seen this on older brake hoses. It could either the front sides or the rear. JMO


    X2

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