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Drum brakes lock up as they heat up

Discussion in 'The Hokey Ass Message Board' started by mack57, Aug 12, 2014.

  1. mack57
    Joined: Apr 17, 2013
    Posts: 176


    Hi all,
    Here's another brake question. 4 wheel drum brakes working perfect until they heat up. The pedal gets hard and the brakes bind seemingly at all 4. As they cool they release and work fine.....
    Any thoughts?

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  2. squirrel
    Joined: Sep 23, 2004
    Posts: 48,235


    old hoses that are collapsed, or the bypass hole in the master cylinder is plugged, or the pedal does not have any free play.
  3. any of the lines close to the exhaust?
  4. mgtstumpy
    Joined: Jul 20, 2006
    Posts: 8,716


    Years ago we chamfered the leading and trailing edges of the brake shoes as they had a tendency to expand more than rest of shoes. A simple idea?

  5. BJR
    Joined: Mar 11, 2005
    Posts: 6,826


    This covers all the things to check for your problem. Replace the old brake hoses, if not the problem they are dangerous. Check to see that the pedal has a little free play in it before it contacts the master cylinder piston. If those 2 things do not fix it, replace the master cylinder.
  6. Rusty O'Toole
    Joined: Sep 17, 2006
    Posts: 9,487

    Rusty O'Toole

    Most likely not enough free play in the pedal. The master cylinder piston must retract all the way to release pressure. If this does not happen the brakes will drag, which produces heat, which increases pressure, which causes the brakes to drag more, which increases pressure etc etc. If you keep going long enough you can burn the brakes right out.
  7. tractorguy
    Joined: Jan 5, 2008
    Posts: 685


    Mis-adjusted brake light switch will allow switch "plunger" to hold very slight pressure on brake pedal and cause drag on brakes.... then heat.......then more drag......then more heat
  8. Ulu
    Joined: Feb 26, 2014
    Posts: 1,767

    from CenCal

    Just in case, also check the axle bearing play. A worn axle bearing will let the brakes drag too.
  9. This is most likely the problem. Back off the rod adjustment a few turns and try it again.
  10. mack57
    Joined: Apr 17, 2013
    Posts: 176


    Thanks Everyone!! I'll post my results!

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  11. Push rod adjustment. Turn it back in towards the dash. Same thing happened to me on my 61 Ford. Looked at the shop manual, Made a template from the pic they had, adjusted the pushrod, and no more brake pedal getting firm as ya drive, or worse yet locked up in you driveway
  12. pontiac
    Joined: Mar 21, 2006
    Posts: 769


    I agree with this also. I've had this problem in the past as well, and generally a few turns of the rod entering the master cylinder fixes the problem.
  13. 35desoto
    Joined: Oct 6, 2009
    Posts: 765


    Another aspect to bear in mind is if the car/pickup has seen little use the wheel cylinders can jam "out" or bind up and not return fully once the pedal pressure is released. I've seen this many times in Mopars where the wheel cylinders were full of Junk on pulling apart. A good clean out, new rubber seals and clean brake fluid can work wonders. When the brakes shoes are "out" they of course keep rubbing against the brake drum and heat up. The expansion of the brake drum through this heat build up means any clearance is lost and the law of friction multiples upwards causing your brakes to stay on until the whole lot cools down and the metal retracts.

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