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Brake Problems - Updated

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by txbluethunder, Sep 30, 2002.

  1. txbluethunder

    txbluethunder 1/2 ton status

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    Issue : Brake pedal goes down about 4 inches until it starts firming up. Then brake light comes on and stays on. The brakes will eventually work but they are very hard and only after all the fluff at the begining.

    Parts Replaced:
    -Master Cylinder
    -Brake Booster
    -Brake Lines (Longer SS Lines)
    -Front Calipers and Pads
    -Rear Wheel Cylinders

    I've bled these through two quarts of fluid so the fluid is pretty new, but it doesn't make a difference. The next step is replacing the proportioning valve but I'd rather not unless I have to. Any thoughts???
     
  2. shane74

    shane74 1/2 ton status

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    Re: Brake Problems

    I have the same problem. I have replaced the master cylinder, and the brakelines too. I have new pads for the front but haven't put them on yet. I'm curious if anyone else has has problem?? Where is the proportioning valve located? Is it the block that the brake lines go into? The one mounted at the front of the truck? Ot is that just a distribution block? One last question, won't poor vacuum from the brake boster cause this as well?
     
  3. txbluethunder

    txbluethunder 1/2 ton status

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    Re: Brake Problems

    i've done the booster test by pumping up the pedel and holding then starting the vehicle and the pedel goes down. i've also tried reving the engine in neutral while i'm trying the brakes with no success. i'm going today to try and get a new proportioning valve. yes its the box on the back of the front crossmember.
     
  4. shane74

    shane74 1/2 ton status

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    Re: Brake Problems

    Please keep me posted! I need to fix my spongy brakes. It wierd, sometimes I have to pump them up, other times they are good and solid. Will the proportioning valve cause this? Also, after installing it, you have to bleed the brake system all over again, correct? GAWD! I feel like an idiot!
     
  5. dyeager535

    dyeager535 1 ton status Premium Member

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    Re: Brake Problems

    Do searches on proportioning valves on here, I bet you'll see many posts blaming the proportioning valve. (about a many as you'll see bad ECM's being blamed, with the same actual failure rate, almost never)

    These things are extremely expensive, and almost *never* the problem. They are extremely simple devices, and if you ask me, chances are its working alright if your brake light is coming on, thats the valve moving, telling you there is some sort of pressure problem front or rear. You can depress the small button on the side of the valve to make SURE its centered, but again, from my understanding, if the light isn't on, the valve IS centered, and doesn't need depressed.
     
  6. txbluethunder

    txbluethunder 1/2 ton status

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    Re: Brake Problems

    well i just checked with chevy...and for $100 bucks i'll take it to my buddies shop instead. i will definately let you know how it turns out.
     
  7. sarazk5

    sarazk5 1/2 ton status

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    Re: Brake Problems

    I had this problem.. replaced everything! Was told no way it could be the proportioning valve... One day it just went away. Light hasn't been on in about a year now! Weird!
     
  8. txbluethunder

    txbluethunder 1/2 ton status

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    Re: Brake Problems

    update - i have now replaced the brake booster as well...no change.
     
  9. 87GMCJimmy

    87GMCJimmy 1/2 ton status

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    I had this same problem but with out the brake light coming on. It went away after I replaced the rear shoes and adjusted them. If your shoes are new maybe your adjuster is way loose. Hope this helps!

    Ok now which graemlin am I going to use............ /forums/images/graemlins/ears.gif Goofy but o'well.

    later
    Mike
     
  10. Blue85

    Blue85 Troll Premium Member

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    Re: Brake Problems

    Isn't this just air in the system somewhere? While the prop valves don't fail very often, I think that they are able to get air trapped in them. Have you tried reverse bleeding the system? I have heard a lot of stories of that giving rock hard pedals after many quarts of regular bleeding that didn't help. Air does want to travel upward, after all.
     
  11. imiceman44

    imiceman44 1 ton status

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    Re: Brake Problems

    I agree that most of the times air is trapped in the system and the only way I was able to fix it was (and that was a suggestion from one of my mechanic buddie) to go downhill on a long road and pumping the brakes regularly, the air trapped should move back up to the master cylinder.
    Now to your original problem, I had that once and it seemed that when I bleed the system the only place I do get any air was on the right rear, and after bleeding it it was fine for a couple of days, until I checked the self adjusting rear, it was not working right and the brake shoes were getting far from the drums and the pistons on a hard brake would get out too far, letting air in.
    Well I fixed that problem and brakes were fine after that. Before finding the problem I replaced Master , proportionning, pads and shoes, cylinders and lines, nothing worked untill I replaced the self adjusting system.
    IceMan
     
  12. txbluethunder

    txbluethunder 1/2 ton status

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    Re: Brake Problems

    well i'd like to thank everyone's help on this one...after a suggestion from Billy Ray I started looking at the rear brake shoes. the same issue as imiceman44 had, the rear auto-adjusters were not functioning correctly. after realizing that the drums about fell off with no effort i tightened up the rear brakes till i could just barely get the rear drum back on and now it stops on a dime with minimal brake travel. it also fixed most of my right side pulling while on the brakes.
     
  13. shane74

    shane74 1/2 ton status

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    Re: Brake Problems

    Looks like I'll be checking mine this weekend! Maybe I'll throw on the pads I have had sitting in a box for a few months. /forums/images/graemlins/tongue.gif lol..
     
  14. txbluethunder

    txbluethunder 1/2 ton status

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    Re: Brake Problems

    i would say buy a couple cans of brake cleaner and put just a dab of grease on the auto adjuster's threads.
     

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