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Most Annoying Brake Problem Ever! Help!

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by pontiacratrod, Dec 8, 2006.

  1. pontiacratrod

    pontiacratrod Registered Member

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    howdy,
    this is my first post here, and i am kind of desperate. ill try to describe in as much detail as possible. last year i bought a 1984 c20 3/4 ton 2wd suburban for $500. brakes worked okay throughout winter, stopped in the snow and wet weather better than my cars. noticing some unusual wear on the pads i suspected a sticking caliper so i just replaced both left and right calipers, hardware and pads. brakes are still okay, but not great. around march i noticed low fluid level in the master, and had spongy brakes so i checked out the wheel cylinders. sure enough they were leaking, so i put in rebuilt ones. couple weeks later, its raining out, and i had to panic stop because someone slammed on there brakes in front of me. my front brakes locked up and i skidded into the guy. pissed off i took it to my buddy and had him do the brakes. said that the parking brake was stuck and ended up burning up the drums and shoes and the wheel cylinder pistons had popped out again. had the drums cut to spec, put new shoes & hardware on. took it out for spin. no change. brakes are still crap. if i brake normal its ok. if i put even a little more pressure on the pedal, the fronts lock up and i skid. ive gone through more than a few stop signs because of this. ive had three shops look at this. no one can figure it out. they all tell me that the rear is not adjusted properly, that there isnt enough drag and that the drums shouldnt just come off w/out backing off the adjusters. so they adjust them up and i end up locking and smoking the rear drums because the drag is so bad. so each time we end up having to back off the adjusters so that there is no drag. also i would like to point out that twice now, in the last year ive been on the expressway and it felt like the rear brakes were overheating and starting to lock on me. id hit the brake a couple times to slow down to a stop and then it would smooth out and go away completely. now... things ive noticed that perplexed me:
    1: master cylinder and power booster flex up and out from the firewall an excessive amount went the brake is depressed. firewall doesnt look like it is moving though...
    2. pedal always feels "okay" not too hard no too soft. doesnt sink or fade. unless you were to try to stop fast you would think that they are perfectly operating brakes.
    3. secondary shoe has half as much lining as the primary shoe. (im not sure if they come like this, because i didnt look when i originally installed them)

    things that have not yet been replaced: master cylinder, power booster, prop valve, brakes hoses front and rear.

    i hope this is enough to accurately describe my problem and maybe get an answer to whats going on. im about ready to shove a shotgun barrel down my throat.
    thanks.... :confused::doah:
     
  2. Can Can

    Can Can Pusher Man Staff Member Super Moderator

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    Have you bled the brakes and reset the proportioning valve?
     
  3. pontiacratrod

    pontiacratrod Registered Member

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    the last time the brakes were worked on, were at my friends shop and i insisted that the brakes be bled to cover the bases. i highly doubt that he reset the prop valve cause he didnt understand why i wanted him to bleed the brakes. how would i reset it correctly, and why would this cause a failure like im describing?
     
  4. BadBob

    BadBob 1/2 ton status

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    You might think about replacing the flex lines if they're older. Sometimes they'll go bad internally and pinch shut inside, and cause all kinds of annoying crap to happen.
     
  5. Thunder

    Thunder 3/4 ton status

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    Replace rubber lines, Bleed system again, Also I think I would go ahead replace the proportioning valve. Sounds to me like it is bad. Fronts locking up befor the rears start braking is a symptom of a bad porp valve. Acually IIRC think it is refered to as a combination valve. Best get one from a Chevy/GM dealer
     
  6. BadBob

    BadBob 1/2 ton status

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    I'm pretty sure that the front brakes are intended to reach lock up first. If the rears lock up first, it'll want to swap ends. It's a PITA on a truck since you have to account for cargo.
     

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