1. '79 CJ problem with breaks! NEED HELP!

    How's it going, new to the site.

    So I bought a 1979 CJ7 for $2000, new paintjob, new tires, rug inside, all I needed to do was clean it up a little. One problem that the jeep had was the breaks. We thought all we had to do was bleed them. We were also wrong. I ended up buying a new master cylinder, I've bled the brakes 3 times. It still won't stop. While the car is off and you pumps the brakes they feel as if they are working, but as soon as you turn the car on, it's as if breaks didn't esixt. So before I go wasting money on crap, might aswell see if anybody here knows what's wrong with it. Please help me, if you can't then point me to someone who can.


  2. Re: '79 CJ problem with breaks! NEED HELP!

    see if this helps:
    there should be a tapered bolt located at the bottom of the brake drum (im guessing thats the way your jeep is but i have seen other designs). jack one rear wheel up at a time the turn by hand and tighten bolt until brakes grab then back of bolt 1/2 turn. do this to both rear brakes. (bolt should have a square head) if this doent work get back with us and tell us how you bleeding the brakes?

  3. #3

    Re: '79 CJ problem with breaks! NEED HELP!

    hey thanks for answering I'm going to do that as soon as I get a chance and I'll let you know how it goes! thanks again

  4. #4

    Re: '79 CJ problem with breaks! NEED HELP!

    If the Jeep has been sitting for a while you might consider changing the rear wheel cylinders. They might leak soon after putting the Jeep in service (assuming you have front disk - if not changing all four wheel cylinders is a good idea) . Be sure all of the brakelines are in good condition. If the Jeep is rusty check the lines carefully. I don't know if your Jeep is the same but my 78 CJ 7 had a little bleeding pin on the proportioning block. When you bleed the brakes you need to hold out the pin. This pin has a little groove in it - a little clip was used to hold it out by the groove. You'll have to make something up to hold the pin (the clip was a special AMC tool) . If I recall, the pin is at the end of the proportioning block, facing forward (but that's a very old memory ) . It's hard to bleed the air out "by hand" unless you hold out the pin. Be sure to release the pin when done. If you pressure bleed the system you might not have to worry about the pin. There is enough pressure and volume to get by it. You can rent a pressure bleeder or have it done. This should get all of the air out. Best of luck - John

  5. #5

    Re: '79 CJ problem with breaks! NEED HELP!

    I was thinking wheel cylinders too. But, If they feel weak when it's running...could it be a vaccum problem?

  6. Re: '79 CJ problem with breaks! NEED HELP!

    good point...are the front brake disks?

    my thought was that the brake slave cylinders were being pulled in by the brake shoe springs so the master cylinder didnt have enoght oil to push the shoes all the way out. by adjusting the brakes shoes as close to the drum as possible there should be enoght oil to push the shoes out. if the jeep is old school front drum brakes then all the brakes would need to be adjusted.

  7. #7
    Join Date
    Nov 2005
    Albany~town, Oregon

    Re: '79 CJ problem with breaks! NEED HELP!

    Not on 'Black Betty' but on my van years ago we found a similar situation and it turned out the diaphragm inside the brake booster had a tear.
    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).

  8. #8
    Join Date
    Aug 2009

    Re: '79 CJ problem with breaks! NEED HELP!

    sounds like a bad proportioning valve

    54CJ3B ,76DJ5RHD , 81DJ5RHD, 88XJ , (It's)93XJRHD(Alive), 06KJ ,

  9. Re: '79 CJ problem with breaks! NEED HELP!

    I am not certain your '79 CJ has Power Brakes. One of my '84 CJ-7s has no Power Brakes, so I am not certain this is your problem. Without listening to it, I would suspect the booster diaphragm if stopping is difficult and possible with great force. However, you did not mention you had any trouble keeping it running at idle. A perforated brake booster diaphragm would be hissing and provide a leak that causes it to run very lean, especially at idle. You could disconnect the booster and plug the vacumme line, if it makes any difference in idle you probably have a leak.

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