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Brakes locked up

Discussion in 'Early CJ5 and CJ6 Tech' started by Cooper, May 19, 2010.

  1. May 19, 2010
    Cooper

    Cooper New Member

    Ludington, MI
    Joined:
    Feb 1, 2003
    Messages:
    27
    I had my CJ5 out for a ride the other day and the brakes locked up. Will heat from the exhaust pipe cause this? I was parked with the jeep running for about 20 minutes. I replaced everything about two years ago and the pedal has never had much travel to it. It only moves about an inch and its hard as a rock. I was able to backup and they seemed to free up a bit so I drove about 2 miles home but there was definetly a drag. I'm not sure where I should start looking. Any ideas?
     
  2. May 20, 2010
    uncamonkey

    uncamonkey Member

    Greeley CO
    Joined:
    Jun 2, 2009
    Messages:
    2,104
    My first guess is to check the rod from the brake pedal arm to the master brake cylinder.
    There should be a little play in it so the plunger can return correctly, releasing the pressure in the system.
     
  3. May 20, 2010
    jhuey

    jhuey Michigan Jeeper!

    Indian River...
    Joined:
    Apr 9, 2004
    Messages:
    415
    Sometimes lack of travel and locking up brakes can be wheel cylinder pistons stuck. My DJ has this issue when sitting for a while. I am going to rebuild with new wheel cylinders and use silicone brake fluid.
     
  4. May 20, 2010
    AKCJ

    AKCJ Active Member

    Fairbanks, Alaska
    Joined:
    Aug 12, 2003
    Messages:
    1,035
    In theory, air in the line would expand with heat so it is possible for exhaust heat to put on the brakes.

    OTOH, you say that the pedal is hard which would indicate no air in the system.

    Maybe the brakes are adjusted very close and maybe there's a little bit of air in the line? Probably worth it to bleed the brakes just as a double check.
     
  5. May 20, 2010
    nickmil

    nickmil In mothballs.

    Happy Valley, OR
    Joined:
    Sep 23, 2002
    Messages:
    12,529
    Crack open a bleeder screw and see if fluid squirts out under pressure. If so then that's a sign the brakes are being held on by hydraulic pressure. Fluid getting hot and expanding, reservoir vent plugged, not enough play in the push rod, etc. can all cause this. If fluid just dribbles out not under pressure then I'd suspect shoes adjusted too tight, stuck caliper/wheel cylinder, something like that.
     
  6. May 20, 2010
    gibson-d@sbcglobal.net

    gibson-d@sbcglobal.net Member

    Houston, TX
    Joined:
    Feb 11, 2007
    Messages:
    93
    When I installed a reman master cylinder there was a thin washer where the pushrod gos, I left it in and I had the same problem as you are having. I removed the washer which was binding the pushrod/piston, it's been years and no problems.
     
  7. May 20, 2010
    jeep2003

    jeep2003 Well-Known Member

    Upstate NY
    Joined:
    May 30, 2006
    Messages:
    1,918
    i had that happen on my 2a once. The pedal was really stuck feeling almost like it was rusted solid. It got really hard to push and once the brakes were applied it wouldnt release. I flushed the system with new fluid and made a little heat sheild for the mc and all was good
     
  8. May 20, 2010
    Cooper

    Cooper New Member

    Ludington, MI
    Joined:
    Feb 1, 2003
    Messages:
    27
    Thanks guys. Looks like its time to get dirty. One thing I forgot was I had to install a master battery breaker switch because the brake lights would come on by themselves. I never could figure out why but thought it had something to do with the hard pedal. Looks like it could be any number of things so I will start at the bleeders and work my way to the master cylinder. Gibson, is the washer on the master cylinder pretty obvious? Also I'm assuming that the FSM describes how to adjust the brakes. I need to find mine.
     
  9. May 21, 2010
    nickmil

    nickmil In mothballs.

    Happy Valley, OR
    Joined:
    Sep 23, 2002
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    12,529
    If the brake lights are staying on that could be an indicator that hydraulic pressure is being held on the system as the brake light switch is pressure activated (if your system is stock).
     
  10. May 21, 2010
    dohc281

    dohc281 It is what it is.

    Laurel Springs, N.J.
    Joined:
    Dec 30, 2004
    Messages:
    605
    When I installed the dual reservoir mc in mine I didn't cut the rod down enough and had that problem, when I shortened it it went away.
     
  11. May 21, 2010
    Chewy

    Chewy New Member

    Southern Michigan
    Joined:
    Mar 10, 2008
    Messages:
    22
    I had a similar problem with a new master cylinder. Ended up that the plunger was not returning all the way to release pressure. If I bled off the pressure, it would work fine for a while, then start to drag really bad after a few brake applications and the brake lights stayed on. After removal of the previously mentioned washer, it has worked.
     
  12. May 22, 2010
    Cooper

    Cooper New Member

    Ludington, MI
    Joined:
    Feb 1, 2003
    Messages:
    27
    Is that washer held in with a wire snap ring? I pulled the boot back last night and I can see a washer on the end of the master cylinder. It has a wire snap ring holding it into place. Going to dig in farther tonight. Thanks for all the info so far.
     
  13. May 22, 2010
    Walt Couch

    Walt Couch sidehill Cordele, Ga. 2024 Sponsor 2023 Sponsor 2022 Sponsor

    cordele, Ga.
    Joined:
    Mar 29, 2007
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    Be careful there. The plunger inside is spring loaded. You remove that lock ring and the guts will shoot out at you. Be sure you can maintain pressure on the plunger and keep it inside the master cylinder at all times.
     
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