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Cj5 Master Cylinder Stuck

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

  1. Jan 27, 2022
    EDDY ARNOLD

    EDDY ARNOLD Member

    71655
    Joined:
    Apr 6, 2021
    Messages:
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    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.
     
  2. Jan 27, 2022
    Jw60

    Jw60 WRPD855 2022 Sponsor 2021 Sponsor 2020 Sponsor

    Sedalia MO.
    Joined:
    Apr 8, 2008
    Messages:
    2,688
    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.
     
    Rick Whitson and dozerjim like this.
  3. Jan 27, 2022
    KJSR

    KJSR New Member

    Utah
    Joined:
    Jun 9, 2021
    Messages:
    26
    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?
     
  4. Jan 27, 2022
    Howard Eisenhauer

    Howard Eisenhauer Super Moderator Staff Member

    Tantallon, Nova...
    Joined:
    Nov 22, 2003
    Messages:
    7,498
    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.
     
    Glenn, PeteL, Twin2 and 3 others like this.
  5. Jan 28, 2022
    EDDY ARNOLD

    EDDY ARNOLD Member

    71655
    Joined:
    Apr 6, 2021
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    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??
     
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