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Help! Disc brakes problems....

Discussion in 'The Hokey Ass Message Board' started by usedall9, Oct 10, 2007.

  1. usedall9
    Joined: Oct 30, 2006
    Posts: 423

    usedall9
    Member

    Hey, there thanks for looking. My buddies got a 54' ford w/ power disc brakes. The problem is that they pump up automaticly? to where there is no pedal action "like stepping on a rock", and the front discs are of course locking up? What could be some possible senario's "spelling?"... He's bringing it by this weekend and I'd like to have some places to start...Thanks again for any input.
     
  2. budd
    Joined: Oct 31, 2006
    Posts: 3,478

    budd
    Member

    so you leave the car sit for a few days and get in and the pedal seems normal?, you pump the brakes and in just a few pumps the pedal is hard?, or with the car not running the brakes seem fine and as soon as you start the car the pedal goes hard?
     
  3. Tinman
    Joined: Mar 6, 2001
    Posts: 963

    Tinman
    Member
    from Orange, CA

    Re-bleed the system to get any trapped air out... I would guess you're getting heat expansion somewhere and that it's applying the front brakes, adding more heat, applying more brakes, etc...

    Is this a remote booster system? Dot 3 or 5 fluid?
     
  4. Mudslinger
    Joined: Aug 3, 2005
    Posts: 1,964

    Mudslinger
    Member

    I had heat expansion on my 49 with drums. It was a rear line next to my brand new dual exhaust. It wasnt touching just right next to the pipe. I bent the line over just a touch and no more rock pedal.
     

  5. squirrel
    Joined: Sep 23, 2004
    Posts: 55,931

    squirrel
    Member

    other things to check:

    old brake hoses
    no pedal free play (or no free play between booster and m/c)
    clogged relief hole in m/c


    there are a few more possible causes that I forget, but we discuss this problem every month or two.
     
  6. Gerry Moe
    Joined: Jan 29, 2006
    Posts: 498

    Gerry Moe
    Member

    Check the brake calipers, bleeder should be on top, chevk booster for vac leaks.
     
  7. Mine was related to the lack of freeplay between the mastercylinder and the pedal assembly.

    Also should have a return spring on the pedal so that it really does return and doesn't accidently pump itself up on bumpy roads...!
     
  8. brewsir
    Joined: Mar 4, 2001
    Posts: 3,278

    brewsir
    Member

    You really should be a little more specific on the problem....it would make it easier to make suggestions....Does it happen after a short drive or when it is just sitting in the garage all by itself....after you step on the pedal.......???
     
  9. usedall9
    Joined: Oct 30, 2006
    Posts: 423

    usedall9
    Member

    No, bleed them then there fine...Fire it up and it seems like the power booster goes overboard in just a matter of minutes. Then stays that way running or not (I believe?) Until bleed again....
    Thanks,
    Graham
     
  10. usedall9
    Joined: Oct 30, 2006
    Posts: 423

    usedall9
    Member

    I pretty sure He's bleed them several times. He did'nt build the car, the fella that did, did a great job on the body type stuff, but we've been constantly chasing mechanical gremilin's. Not sure what fluid he's running though.
    Thanks
     
  11. usedall9
    Joined: Oct 30, 2006
    Posts: 423

    usedall9
    Member

    other things to check:

    old brake hoses
    no pedal free play (or no free play between booster and m/c)
    clogged relief hole in m/c
    there are a few more possible causes that I forget, but we discuss this problem every month or two.
    <!-- / message --><!-- sig -->
    Thanks Squirrel,
    All parts are brand new, Car probably has less than 1500 miles on everything. Was a frame off resto. There is NO pedal free play at all!

    Mine was related to the lack of freeplay between the mastercylinder and the pedal assembly.

    Also should have a return spring on the pedal so that it really does return and doesn't accidently pump itself up on bumpy roads...!

    No return sping on it, I'm sure...This is something to look into.
    Thanks WingNutz

    You really should be a little more specific on the problem....it would make it easier to make suggestions....Does it happen after a short drive or when it is just sitting in the garage all by itself....after you step on the pedal.......???

    I'm Trying, like I stated, I have'nt had a chance to look @ it yet. Just looking for possible places to start. Problems people might have had when they were working out the kinks on a new power brake system. Thanks for responding, I know your trying to help.

    Graham
     
  12. Several years ago a friend's Cadillac had a booster that started acting up.
    It was a recently purchased booster from A-Z.
    When he would stop at a light, he would sometimes feel something like the pedal being moved or pulled on by something ever so slightly. When the light turned green and he released the pedal, sometimes the car would not move, or sometimes it would leave the stoplight with a feeling that the brakes were dragging.
    Turning off the engine would cure it, then the brakes would operate normally again- for a while.

    He brought it by my house. I tried it out several times and found nothing.
    Right about the time he was going to leave, it happened again.
    I barely heard a slight vacuum sound, and saw the pedal pushrod move as if it was being pulled into the booster a small amount.
    It was as if the booster had a badly adjusted valve that would once in a while act as a hair-trigger.
    Nothing in the linkage was binding. Return springs were adequate. The pushrod was not overlength.

    We took the booster back to trade it on another one and it hasn't happened since.
     
  13. The clearance on the rod between the booster and master cylinder is a likely culprit but the rod from teh pedal to teh booster can cause the problem you describe also. If the rod from the pedal to the booster is not allowing the booster to return fully to rest it will cause your brakes to gradually apply and possibly lock up. An easy check is to remove the rod going from the pedal to the booster and then start the engine. If the problem goes away then you need to shorten the rod by adjusting or grinding the end shorter a little at a time until it works. I had a similar problem once on a after market under the floor brake setup.
     
  14. usedall9
    Joined: Oct 30, 2006
    Posts: 423

    usedall9
    Member

    Thanks guys,
    All this is good info. I appreciate any and all input.
     

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