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Brake Question

Discussion in '1969-1972 K5 Blazer | Truck | Suburban' started by Klef72K5, Jan 8, 2002.

  1. Klef72K5

    Klef72K5 1/2 ton status

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    I put on a new vaccume booster and a new master cylinder. my brakes were very hard before I did all of this. They are still hard but not as bad. Now I notice when I really stand on the brakes my brake light comes on. What does this light mean?
    When I bled the brakes I didn't do anything to the proportioning valve. Would that make my brakes hard and the light come on by not putting the spacer behind the stem on the proportioning valve? What exactly does that stem do?

    <a target="_blank" href=http://wsphotofews.excite.com/031/rw/Jo/og/t488200.jpg>http://wsphotofews.excite.com/031/rw/Jo/og/t488200.jpg</a>
     
  2. Triaged

    Triaged 1/2 ton status

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    The brake light comes on when there is a inbalance in part of your brake hydrolic system. It could be air in the lines or a leak somewere.

    '71 Blazer CST w/ a 400sbc, 4" lift, 36" Supper Swampers, and alot of rust
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  3. cleszkie

    cleszkie 1/2 ton status

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    You need to hold the metering valve pin in when you bleed the brakes. If you do not do this, the system will not get bled. If you do not hold the pin in when you proceed to open up a bleeder valve and pump the brakes, the system will interpret the open bleeder as a sytem failure of either the front or rear system (depending on which bleeder valve you have opened). The combination valve will automatically shut down flow through the "open" system, routing all braking power to the closed system. This effectively prevents you from purging the open system. Hold the pin in and you will solve the brake light problem and funky peddle.
     
  4. Klef72K5

    Klef72K5 1/2 ton status

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    That dang thing will make my brakes hard ??????
    I hope so anyways!

    <a target="_blank" href=http://wsphotofews.excite.com/031/rw/Jo/og/t488200.jpg>http://wsphotofews.excite.com/031/rw/Jo/og/t488200.jpg</a>
     
  5. Steve_Chin

    Steve_Chin 1/2 ton status

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    Sounds like the spool in the combination valve needs to be re-centered. You can re-center it by carefully taking the valve apart, removing all the parts, cleaning it, then reassembling it. You must then bleed the entire system with the button held in to prevent this from happening again.
     
  6. Klef72K5

    Klef72K5 1/2 ton status

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    Hey Steve this is a old post, but I finally got some time to work on the blazer. How far will the pin push in? How far should it be sticking out? I tried to push mine in and had no luck. Is there a trick?
     
  7. Triaged

    Triaged 1/2 ton status

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    It doesn't really push in any...it is more like held in. When you bleed the brakes it will try to push out...you are just trying to hold it from moving. It doesn't take much pressure either.
     
  8. Klef72K5

    Klef72K5 1/2 ton status

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    I almost got a BFH to relocate that pin, but I'll try your way first.
     
  9. alta-aj

    alta-aj Registered Member

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    Another way to reset the spool in the proportioning valve is to disconnect the switch wire, remove the switch and use a small screwdriver to recenter the spool. Once there has been an imbalance between the front and back brakes causing the spool to shift, unless you do this the brake light will stay on forever.
     
  10. Klef72K5

    Klef72K5 1/2 ton status

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    The brake light only comes on when I'm really on the pedal hard. They will stay on until I tap the brakes again.
     
  11. Triaged

    Triaged 1/2 ton status

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    The switch that turns the brake light on in centered by springs. It normally re-centers its self after you let off the brake but can get sticky w/ age.
     

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