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  • Intermittent brake failure

    Alright guys, I can usually diagnose vehicle problems pretty well but this one has me a stumped and I don't want to just change out parts hoping it fixes the problem.

    On 2 separate occasions now my brake pedal has gone limp. Not just a soft pedal, I mean it feels like the linkage became disconnect and the pedal swings free. Then the brakes just start working again like nothing ever happened.

    The first time I was on steel hill and thought it was too steep and maybe had an air bubble in the master, as soon as I backed it down in gear and got on flat ground the pedal came back. I topped off the master cyl reservoir completely to the top and thought it solved the issue. Last weekend the same thing happened on a much less steep hill (Kevin was showing us that memorial hill, I forget the guys name). As soon as I turned off the jeep, to hop out and troubleshoot, the pedal pressure came right back with the jeep not running. Never had any other issues with it the rest of the weekend.

    I didnt want to post to facebook because I dont need 100 people just guessing and telling me to replace this or that. Have any of you guys ever ran into anything like this?

    94 Yj, factory vacuum booster. Master cylinder was new from autozone for 2000 dodge 1500. Wilwood adjustable prop valve on rear line. Front brakes are 1992, 1 ton dodge dana 60 (same as 1 ton chevy calipers I assume) and rear are 1977, 3/4 ton chevy disk conversion.

  • #2
    If it feels like the linkage comes off, id start looking under the dash for loose parts. Mine does something similar after using the brakes a lot, like on granny templeton. I never feel like they are gone, just soft.
    Wonder if the master cylinder can get stuck in. that would make the pedal loose.

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    • #3
      anyway you miggt be losing vaccum?
      sigpic

      Keep them on all 4's

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      • #4
        Originally posted by jeepmanjeff
        anyway you miggt be losing vaccum?
        losing vacuum should make the hard, not loose.

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        • #5
          OK I guess I should've started under the dash on checking the linkage, I'll check tonight. I hadn't thought about the master cylinder sticking. That may be possible since my clutch does it all the time. The one issue I have with that theory is I was able to back down off of steel hill as if the brakes were not engaged at all.

          I agree with Kevin, I think losing vacuum would turn it into essentially manual brakes and that's not what the pedal feels like. I'll check all the vacuum fittings and connections just to be sure.

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          • #6
            I haven't figured out exactly why its doing it so infrequently but I believe it has to be the master cylinder. Going to re-bench bleed and see if that keeps it from happening again.

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            • #7
              I would say its the master Cylinder, if you bench bleed it and you continue to get air its junk.
              No need for a Winch...You just have to make it !!

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