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drums brakes building pressure while driving, help needed.

Discussion in 'The Hokey Ass Message Board' started by jhaas63, Aug 17, 2013.

  1. jhaas63
    Joined: Jan 15, 2013
    Posts: 136


    I have a 53 f100. Last year, the master cylinder, brake lines, hoses and wheel cylinders were all changed. Brakes worked great all spring. However now, they are building up pressure while driving on trips over 5 or 6 miles to the point of basically locking up. After this, if the truck sits for an hour or so, the brakes eventually leak down and you can drive it again. Any idea on what the problem/solution is?
  2. F-6Garagerat
    Joined: Apr 12, 2008
    Posts: 2,652


    Is one of the new lines run close to the exhaust? Just a guess?????
  3. J. A. Miller
    Joined: Dec 30, 2010
    Posts: 1,549

    J. A. Miller
    from Central NY

    Do you have some free play between your pedal arm and the rod going into the master cylinder?
  4. GassersGarage
    Joined: Jul 1, 2007
    Posts: 4,728


    Check your M/C to see if it's overheating. If so, track down the heat source.

  5. Yep. Rod going in to master cylinder is to long. Only the slightest fraction of an inch is all it takes.
  6. 40Standard
    Joined: Jul 30, 2005
    Posts: 5,833

    from Indy

    adjust your brake pedal rod
  7. Vergil
    Joined: Dec 10, 2005
    Posts: 785


    If it doesn't the master cylinder piston will not come out far enough to expose the hole for the brake fluid to transfer back into the reservoir as the fluid heats up expanding and the pushing the brake shoe out against the drum.
  8. First thing to do - when the brakes get to locking up, crack a bleeder to see if there is pressure (careful, the fluid WILL be hot).

    If there is pressure, check next the rod into the master, make sure it is fully retracting and has free-play.

    If all is good there, the relief port in the master is probably plugged. This is the least likely, so last to check.

    BTW, anyone else remember that this was a subject from the Model Garage??

  9. X3 on push rod free play adjustment
  10. TxRat
    Joined: Dec 22, 2004
    Posts: 1,412


    Yep, I'd look for a line close to your exhaust. Had the same problem on my
    Nomad. Routed a new brake line to the rear of the car and routed it differently, no more problems...
    Last edited: Aug 18, 2013
  11. 68vette
    Joined: Jul 28, 2009
    Posts: 306


    The rod going in the Master cylinder is too long....turn it in about 3 turns or so. Problem fixed....if not...2 more turns.

    This has been mentioned a time or two and also the brake pedal should have about 1/4 inch free play before the MC engages if the rod is adjusted properly.
  12. lesbliss
    Joined: May 16, 2009
    Posts: 10

    from Canby OR

    Had exactly the same thing happening with my 51 Merc. Rebuilt everything and it still happened. Finally installed a NEW master cylinder and problem solved. For some reason rebuilding the old MC didn't solve problem

  13. 55willys
    Joined: Dec 7, 2012
    Posts: 1,615


    Sometimes the brake hose is the culprit. It's liner will collapse and become a check valve not letting the fluid return to the master. Jim (55willys)
  14. stimpy
    Joined: Apr 16, 2006
    Posts: 3,547


    had this happen on a dual hyraulic set up ( hyd over hyd ) on a old chevy straight truck , the return spring on the pedal broke and was pumping up the system as we drove down the road as the pedal bounced back and forth
  15. JohnEvans
    Joined: Apr 13, 2008
    Posts: 4,883

    from Phoenix AZ

    Yep lack of a pedal return spring can cause this issue as well.

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