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RR brake grabby, '87 Burb, tried everything...

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by uglytruk, Feb 11, 2006.

  1. uglytruk

    uglytruk 1/2 ton status

    Joined:
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    IN A JUNKYARD, UNDER A TRUCK*N E Rust Belt
    If it's not one thing, it's another. I just did a ton of suspension and brake work on my newly aquired 87 3/4 ton 6.2 Burb. When I test drove it last week, the right rear brake was "grabby". So even though pulling the drum showed no oil or weird stuff, I changed the shoes anyways. I ground off the "lip" to make it easier to re-install the drums, (13"), ground down the wear spots on the backing plates and made sure everything was up to snuff. Anti-sieze in all the right places, cracked open the bleeders to let the fresh fluid run through, and new calipers in front.
    The RR ebrake cable was toast, so I installed a slightly shorter one, and adjusted the whole lot carefully. And that's where the trouble began. The return spring on the front (cab) cable is weak, so the ebrake pedal won't return to put out the light. No problem, I 'll put a wire clamp on to "shorten" the spring. A test drive wasn't promising. The RR started to grab after a few easy miles, I backed off the ebrake, thinking it was a little tight. No dice. This morning, (5f), I pulled the drum off, expecting to have to back off the shoes or maybe a sticky cylinder, Nope, drum came right off! Weird! I double checked free travel of cylinder pistons, smooth travel of shoes, cracked bleeder, yadda, yadda. Thinking I was just having bad luck, I traveled 40 miles to Vermont. Upon arrival, it's doing it again. Didn't touch ebrake, cold outside, no mountain decents, just grabby, slightly applied feel. I cracked the RR bleeder, a bit of oil trickled out, and off came the drum again in a bookstore lot. Again I expected the drum to be held by the shoes, but no! What's going on? [​IMG] I put a small ViceGrip on the rear rubber hose, cracked the bleeders, and drove 30 or so Interstate and 2ndary miles to the ferry to cross the lake. and it did it again! Thinking some oil leaked past the ViceGrips, I left the bleeders open, but the RR was still doing its weird dance.

    OK, I give up. Maybe I should try a different drum. I have a '79 2wd 3/4t. 16.5 wheels, but same drum? If it was the master cyl, it would affect BOTH back brakes, not just the RR, right? Backing up makes it worse, and I got the leading/trailing shoes right. Remember, the previous shoes exibited similar behaviour.

    I'm formerly an ASE licenced mechanic, so this problem really stumps me...
     
  2. Muddytazz

    Muddytazz 1 ton status

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    I had a similar problem years ago on an old truck I used to own. Tried and tried what I thought was everything to fix it. Finally gave up on it and took it in to a shop. They pressure bled the complete system and the problem was solved. Apparently I had a line issue to 1 of my tires(can't remember which one it was tho right not).
     

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