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Cj5 Master Cylinder Stuck

Discussion in 'Early CJ5 and CJ6 Tech' started by EDDY ARNOLD, Jan 27, 2022.

  1. EDDY ARNOLD

    EDDY ARNOLD Member

    69 cj5 v6 with new master cylinder, brake cylinders and shoes. Worked fine for 6 months. Let set up last month and barely made it back home all 4 wheels locking up. Loosened lines and rolls again.
    Fluid looks new.
     
    EDDY ARNOLD, Jan 27, 2022
    #1
  2. Jw60

    Jw60 That guy 2024 Sponsor 2023 Sponsor 2022 Sponsor

    Sounds like a residual pressure valve issue or stuck pistons.
    Maybe crud build up or oxidation in master cylinder. Try flushing the system out the cylinder bleeders and get fresh fluid in there. Note condition of bleed fluid.
     
    Jw60, Jan 27, 2022
    #2
    Rick Whitson and dozerjim like this.
  3. KJSR

    KJSR New Member

    Sounds like your rod going into the master cylinder is not adjusted properly. How much clearance is there in the rod before it hits the plunger in the master? Is the linkage free of binding?
     
    KJSR, Jan 27, 2022
    #3
  4. Howard Eisenhauer

    Howard Eisenhauer Administrator Staff Member

    If the m/c piston doesn't return all the way to the rear stop then the ports to the reservoir don't get uncovered diss-allowing fluid to move out of the lines. This becomes important if one of the brakes is dragging & making heat- that heat makes the fluid expand and, since it can't bleed back into the reservoirs, line pressure builds up pushing the other brake shoes/pads and making even more heat. Eventually the brakes lock up & stay that way until the fluid cools off.

    So- why isn't the M/C piston returning all the way aft?

    Sticky piston?

    Miss adjusted push rod?

    Something interfering with the pedal linkage?​

    Those are the things you need to be looking at.
     
    Howard Eisenhauer, Jan 27, 2022
    #4
    Glenn, PeteL, Twin2 and 3 others like this.
  5. EDDY ARNOLD

    EDDY ARNOLD Member

    Will check worn out linkage and m/c design from hell. Brakes worked fine 6 months until let set up for 1-2 months. Never adjusted master push rod??
     
    EDDY ARNOLD, Jan 28, 2022
    #5