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Thread: Brake Lock Up

  1. #1
    Commander Member Joe Tondu's Avatar
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    Brake Lock Up

    After replacing U joints, re packing axle bearings, replacing outer rear axle seals, adjusting axle end play, and bleeding brake line, the test drive was cut short due to extreme brake sensitivity. Just the slightest touch of the pedal sent the car screeching to a skidding halt. I think the problem is in the right wheel. I've taken it apart twice to inspect, but nothing looks amiss. Shoes have been carefully adjusted and so has the parking brake. Any ideas? Thanks.
    1950 Champion
    1962 MGA

  2. #2
    Speedster Member
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    Are the front and rear shoes in the proper location on both sides. Any brake fluid or grease on the linings.


    Hawkowner

  3. #3
    Commander Member Joe Tondu's Avatar
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    Looks like all shoes are in proper order. No grease or fluid on shoes.
    1950 Champion
    1962 MGA

  4. #4
    President Member thunderations's Avatar
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    I've noted that many brake problems of this sort have been traced to the hill holder, if there is one. Bleeding it may help.
    Others having worked on these will soon chime in, I'm sure. The proper adjusting of the brakes is critical on this application, but it seems you are already aware of this.
    Best of luck getting it corrected.
    1966 Daytona (The First One)
    1950 Champion Convertible
    1950 Champion 4Dr
    1957 Thunderbird

  5. #5
    Commander Member
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    I would take another look at the Primary shoe and secondary shoe. They can get overlooked and installed incorrectly. GOOD LUCK

  6. #6
    President Member
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    Also, double check to make sure the adjustment between the pedal and M/C is NOT too tight.

    Jim
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  7. #7
    Silver Hawk Member JoeHall's Avatar
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    Sounds like contamination. I'd double check the shoes and drums for even a trace of oil, grease or brake fluid contamination. Lightly sand the shoes with 220 grit sand paper, and look for, "wet spots" to show through the dry surface in a few minutes. I'd wipe the insides of the drums clean, then wipe down with lacquer thinner, and then wipe again after dry. If the shoes are not too contaminated, they will probably be OK, but grab initially for a few miles. Riding the brakes, off and on, for several miles, at 35-40 MPH often helps dry them out.

    Good luck !

  8. #8
    Commander Member
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    A few pictures may help. Definitely clean the shoes if they had been contaminated. Check tire pressure. GOOD LUCK

  9. #9
    Silver Hawk Member jclary's Avatar
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    Just going on the info from your initial post, you mention the right wheel as the one locking up. So, how do you get it to release? Do you back up slightly? That's how I would do it when the brakes on my Land Cruiser would temporarily lock after the car had sat for weeks. Another thing to look at is the brake shoe rub blocks, (locator bosses, or any number of names I've heard them called) stamped into the backing plates. I've heard others state that theirs had worn grooves in them causing the brake shoes to snag and bind.

    Not to state the obvious, but locking brakes are a sure indication the brakes are getting applied, but not releasing. I would really suspect a hill holder if both brakes locked, but not only one. There was a friend of mine,(RIP) who, not being mechanically inclined, bought a Studebaker with a hill holder that was not hooked up. His mechanic accidentally bumped the linkage arm on the hill holder when greasing the car and neither of them knew what caused the brakes to lock up. They called me, and I drove over and found the problem in a few minutes. The mechanic said he had never seen a hill holder. I moved the hill holder arm back to the off position, and told him to try and find the linkage, since it obviously worked.

    In your case, there is something either binding, or mechanically preventing the brake shoe from releasing. You did not mention any action on the brake cylinders except for bleeding. Have you looked behind the rubber cups on the cylinders? Are they free from corrosion? Are both sides of the cylinder clean? If one is corroded, and the other not, the hydraulic pressure will be applied the shoe with the free piston. That could cause the sensitivity to slight pressure, if all the pressure is going to only one shoe due to a cylinder with only one side working. My explanation might be clear as mud, but these "simple" systems are designed to distribute pressure equally. No matter how many degrees you have, or how much experience, they can still drive you nuts trying to identify a problem.
    John Clary
    Greer, SC
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    SDC member since 1975

  10. #10
    Commander Member
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    Did you replace the flex brake hose ? If they are old , they may let pressure to the wheel cylinder but not let it return the fluid due to break down of the material .

  11. #11
    President Member
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    Don't be fooled by thinking since the hill holder linkage is in off position the hill holder is not your problem. I chased my tail for days working on a 63 R2 Hawk before realizing the hill holder was still in the circuit since brake fluid still circulates thru it with linkage not connected. I disconnected the brake lines at the hill holder and fabricated a " jumper" brake line. Brake lock up problem solved.

  12. #12
    Commander Member Joe Tondu's Avatar
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    Turns out it was the FRONT wheel. Haven't touched this since 200 miles ago when I installed all new stuff there. So, pulled the drum. Shoes, pads, drums - everything ok. Drum not scored but shoe lining auto adjuster was aweful close to the drum. Readjusted this and since the eccentrics were on the loose side, I tightened these up. Seems to have fixed it, although o have no idea why.
    1950 Champion
    1962 MGA

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