1. #1
    Zam1787's Avatar
    Zam1787 is offline Junior Member
    Join Date
    Sep 2017

    78 cj-5 brake issue

    I have a 1978 jeep cj-5 that I just picked up and I have been going through and narrowing down some things I need to do. One item on my list was the master cylinder was leaking into the tub on the floor, as well as over the top onto the headers.. so I order a master cylinder from advanced auto.. went to install it today, and the rod that attaches to the brake pedal, has a round piece attached to it.. when I put the new master cylinder on, and press the pedal, it pops the lock ring on the inside of the master cylinder. I compared my new and old cylinder and they are exactly the same. Probably the reason it leaked is previous owner tried to fix and ended up with the same issue I'm having.. it fits and lines up.. but when u slowly depress the pedal it only moves an inch.. if u press harder it pops past that lock ring and then has full pedal stroke.. upon releasing it pops back past the lock ring.. wrong part? I uninstalled and installed multiple times.. Anyone else have this issue.. car has no vacuum booster on it (don't know if it came with it or not)

  2. #2
    flatie46's Avatar
    flatie46 is offline Senior Member
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    Jul 2010
    Russellville TN

    Re: 78 cj-5 brake issue

    I replaced the master cyl on my CJ 5 several years back but I wasn't faced with this issue. Sounds like either the wrong rod or wrong master cyl. You could take your rod to the parts store and see what a new one looks like compaired to yours. Maybe it had power brakes at one time and the rod may be different.
    I bought a caliper and had to grind some off the casting to get the wheel to fit over it. Your MC may be made by the same poor quality company.

  3. #3
    superj's Avatar
    superj is offline Senior Member
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    Feb 2010

    Re: 78 cj-5 brake issue

    It sounds like the rod to me.
    no more jeeps at this time. next time it will be a cj with a v8

  4. #4
    Turbogus's Avatar
    Turbogus is offline Senior Member
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    Nov 2005
    Albany~town, Oregon

    Re: 78 cj-5 brake issue

    X3 Mine from NAPA went right in
    Quick fixes are so named for how long they stay fixed.
    If you run out of gas, no matter which way you decide to push, the closest gas station will always be uphill and in the other direction. Corollary: The likelihood of running out increases when all of the nearby gas stations are closed.
    The parts shop that stocks part for Skylab II will not have parts for our year/model of Jeep.
    We cannot accurately judge the trajectory of a speeding critter (cat, dog, sasquatch).

  5. #5
    Empty Pockets's Avatar
    Empty Pockets is offline Junior Member
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    Sep 2017

    Re: 78 cj-5 brake issue

    I can't remember which is which, but on one cylinder, the rod bore in the piston is deeper than the other. Power and standard brake MC's are not interchangeable. If I recall correctly, the PB master rod bore is shallower than the manual cylinder, although it may be the other way around.

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