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'71 Front Drum Brake Issue

Discussion in 'Early CJ5 and CJ6 Tech' started by pblalock, Mar 26, 2013.

  1. Mar 26, 2013
    pblalock

    pblalock New Member

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    May 9, 2012
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    I have a '71 that has been restored. still mostly stock. I am having a problem with the front brakes sticking/dragging. Dana 27 with drum brakes..10" (i'm pretty sure) All new brake parts all the way around ( lines, wheel cyl., m/c, etc) I can bleed them and they seem fine. When I drive it.., after a few stops..the front brakes will start dragging. When applying the brakes, it will yank the jeep (steering wheel) left. Especially if you hit the pedal kinda hard/quick. I have driven back to the garage numerous times and immediately get out and jack the front up and try and roll the wheels. The RIGHT one will be dragging the most and (THIS IS WEIRD) it WILL NOT roll backward!! The left one will have some drag also but will roll either way. I can crack the bleeder and all is well again!! The rears are fine. Very aggrevating and getting not much fun to drive! Any ideas would be greatly appreciated. Thanks
     
    pblalock, Mar 26, 2013
    #1
  2. Mar 26, 2013
    fixitcj5

    fixitcj5 New Member

    San Diego, CA
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    Did you replace the proportioning valve as well? Are the brake shoes adjusted properly?
     
    fixitcj5, Mar 26, 2013
    #2
  3. Mar 26, 2013
    lynn

    lynn Time machine / Early CJ5 HR Rep Staff Member

    Huntingdon PA
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    Self adjuster installed backwards?
     
    lynn, Mar 26, 2013
    #3
  4. Mar 26, 2013
    PeteL

    PeteL If it wasn't for physics, and law enforcement... 2024 Sponsor 2023 Sponsor 2022 Sponsor

    Hills of NH
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    " it WILL NOT roll backward!"

    That seems to say the right-side rear shoe is not retracting, and is self actuating in reverse. Stuck cylinder? Spring detached? Possibly contaminated with grease or fluid?
     
    Last edited: Mar 26, 2013
    PeteL, Mar 26, 2013
    #4
  5. Mar 26, 2013
    Walt Couch

    Walt Couch sidehill Cordele, Ga. 2024 Sponsor 2023 Sponsor 2022 Sponsor

    cordele, Ga.
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    I had that same problem with mine with new wheel cylinders, shoes, etc. Mine was the right front cylinder had formed some kind of rough coating inside the cylinder and the springs could not collapse the shoes. Polished the inside w/600 grit cloth, washed, installed. Has been working fine since. That was a year ago.
     
    Walt Couch, Mar 26, 2013
    #5
  6. Mar 26, 2013
    pblalock

    pblalock New Member

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    In response to fixitcj5's question... I don't have a proportioning valve in the line. I thought the dual m/c was suppose to have one in it for each line.??. I know some people have said it is called a distribution block. don't have that either. Suppose to??
     
    pblalock, Mar 26, 2013
    #6
  7. Mar 26, 2013
    wheelie

    wheelie beeg dummy 2024 Sponsor 2023 Sponsor

    York, PA
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    I would think if it were mechanical in nature (a spring or self adjuster problem, etc.), bleeding the brakes would not reverse/alleviate the problem. Has to be problem in the hydraulics, in my mind. I like Walt's thinking, with the wheel cylinder.
     
    wheelie, Mar 26, 2013
    #7
  8. Mar 26, 2013
    Howard Eisenhauer

    Howard Eisenhauer Administrator Staff Member

    Tantallon, Nova...
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    How much play do you have in the brake pedal? Sounds to me like the MC piston isn't coming back all the way meaning the fluid is trapped in the lines, unable to flow back into the MC. When the fluid heats up it expands, pushing on the brake cylinder, causing the brakes to drag which heats up the fluid more making the problem increasingly worse. This would be fixed by adjusting the push rod to allow the MC piston to come all the way back against it's stop (snap ring in end of cylinder bore).

    H.
     
    Howard Eisenhauer, Mar 26, 2013
    #8
  9. Mar 27, 2013
    Mcruff

    Mcruff Earlycj5 Machinist

    Albertville, AL
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    Sep 22, 2002
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    There was no proportioning valve factory installed before 1972. The brake lines and such were sized accordingly.
    If you replaced the factory dual master cylinder it is possible that there are no residual pressure valves installed or the wrong ones are installed. Some come with them some do not.

    My honest opinion is closer to Howard's idea.
     
    Mcruff, Mar 27, 2013
    #9
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