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caliper bleed issue

Discussion in 'Intermediate CJ-5/6/7/8' started by jeep6275, Feb 6, 2008.

  1. Feb 6, 2008
    jeep6275

    jeep6275 Member

    south east iowa
    Joined:
    Feb 14, 2007
    Messages:
    67
    ok guys i am building a 74 cj5. i swapped the front discs on just like in the article in the technical library.

    all the lines are new and the master cylinder and calipers are new.

    the problem is the front brakes will never build pressure. what i mean is that they seem to bleed but i dont have any movement in them. the drums on back work but the fronts dont seem to.

    i have even changed master cylinders to be sure i got a good one. any advice??

    tia
    jeep
     
  2. Feb 6, 2008
    mcgillacuddy

    mcgillacuddy Member

    Kalama, WA
    Joined:
    Nov 14, 2007
    Messages:
    316
    You used the master cylinder for discs right?
     
  3. Feb 6, 2008
    nickmil

    nickmil In mothballs.

    Happy Valley, OR
    Joined:
    Sep 23, 2002
    Messages:
    12,529
    Are the calipers "clocked" up so the bleeder is at the highest point? If not you have air trapped in there and may never get it out.....
    If you used the drum brake knuckles, the bolt pattern is clocked different than the disc brake knuckles. The normal fix for this is to drill the brackets to clock them up correctly. You can use the spindle as a guide for marking the holes. Nickmil
     
  4. Feb 6, 2008
    jeep6275

    jeep6275 Member

    south east iowa
    Joined:
    Feb 14, 2007
    Messages:
    67
    mcgilla--- the article in the technical library does not say a master cylinder for discs is required. i originally installed exactly like the article reads and then tried a master cylinder from a cj7 with discs. both did the same thing.

    nickmil-- yes calipers are clocked. just like in the pictures in the article.

    thanks for the help so far guys.

    jeep
     
  5. Feb 6, 2008
    mcgillacuddy

    mcgillacuddy Member

    Kalama, WA
    Joined:
    Nov 14, 2007
    Messages:
    316
    Sounds like you have done all the right stuff so far...The reason I asked about the MC was not really because what was happening to you...but the fact that drum brake master cylinders have a residual valve in them...This will make your disc brakes not release like they should (drag)....
    Have you tried to move it around a little...maybe back and forth in your driveway and put on the brake firm a bunch of times? Sometimes if you have some trapped air...it will move it around and then you can bleed it out...I have fought stuff like this for hours...
    Also...your proportioning valve may be messing with you.
     
  6. Feb 6, 2008
    nickmil

    nickmil In mothballs.

    Happy Valley, OR
    Joined:
    Sep 23, 2002
    Messages:
    12,529
    Was the master cylinder bench bled before installation? Have you verified the master cylinder is building pressure at both ports? Is there clearance between the pedal pushrod and master cylinder allowing the primary piston to retract all the way? Any of these can contribute to the problem. Also, when you bleed the brakes, make sure you go slow and easy when pumping the pedal. Going too fast can aerate the fluid adding to the problem.. Might also try gently tapping on the caliper with a small hammer as that can break loose any air bubbles sticking to the inside of the lines and calipers while bleeding. Nickmil
     
    Last edited: Feb 6, 2008
  7. Feb 6, 2008
    jeep6275

    jeep6275 Member

    south east iowa
    Joined:
    Feb 14, 2007
    Messages:
    67
    how much clearance should their be between the rod and master cylinder.

    thanks again

    jeep
     
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