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brake trouble in my 84

Discussion in 'Technical Chat' started by Dark Knight, Sep 8, 2009.

  1. Sep 8, 2009 at 9:59 AM
    #1
    Dark Knight

    Dark Knight [OP] Well-Known Member

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    here are the symptoms:

    firm pedal
    front brakes grab/lock up
    pedal gets more firm as heat builds

    Heres whats already new:

    front calipers
    pads
    rubber brake lines
    master cylinder


    The only thing that is not new is the brake booster. I am leaning towards putting on a new booster because if I take the vacuum line off (plug the line and booster fitting) and then go driving besides having manual brakes they seem to work fine(no grabbing/locking up). After I put the vacuum line back on the booster it worked like it should sporadically for two days then it got real bad and locked up the front to where I could barely drive it home.

    Could it be a problem in the vacuum system somewhere else away from the booster causing this or is there any adjustment in the amount of vacuum?

    Ideas???
     
  2. Sep 8, 2009 at 10:35 AM
    #2
    98tacoma27

    98tacoma27 is gooder 'en chicken Moderator

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    5100's all on fours
    I would check the check valve (if you can) first. Try blowing into the booster through the vacuum hose. You shouldn't be able to.
     
  3. Sep 8, 2009 at 11:19 AM
    #3
    Dark Knight

    Dark Knight [OP] Well-Known Member

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    ok so I know the check valve is a 1 way valve. unhook the end from the carb and blow into the hose (no jokes needed here) towards the booster and that should work??

    that doesnt make good since to me, of coarse i dont really know what i'm doing here, but when I take loose the booster end of the hose there is constant vacuum through the hose(engine running) like the valve is always open in turn always pulling air through. could the check valve be in there backwords???
     
  4. Sep 8, 2009 at 11:20 AM
    #4
    Dark Knight

    Dark Knight [OP] Well-Known Member

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    the check valve is in the middle of the firewall not on the booster itself.... so it could have been messed with at some point.
     
  5. Sep 8, 2009 at 11:27 AM
    #5
    98tacoma27

    98tacoma27 is gooder 'en chicken Moderator

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    There are actually two valves, one in the booster itself. It may be the one in the booster going bad. The theory behind it is when you press the pedal, the valve in the booster opens to allow atmospheric pressure into one side while the vacuum pulls the diaphragm. When you let off the pedal, the spring(s) in the booster pushes it back.
     
  6. Sep 8, 2009 at 11:32 AM
    #6
    Dark Knight

    Dark Knight [OP] Well-Known Member

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    ok so the "inline" valve is correct.... I may just go to auto zone and throw down on a new booster tonight....

    It has to be the check valve in the booster or something in the not equalizing pressure because the pedal is so firm and gets more and more firm locking things up
     
  7. Sep 8, 2009 at 11:34 AM
    #7
    98tacoma27

    98tacoma27 is gooder 'en chicken Moderator

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    5100's all on fours
    That is what it sounds like DK. It's all "suck" .............. Hee hee..... pun intended.
     
  8. Sep 8, 2009 at 11:44 AM
    #8
    Dark Knight

    Dark Knight [OP] Well-Known Member

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    lol thanks for the replies. Plan activated.....
     
  9. Sep 8, 2009 at 3:34 PM
    #9
    Dark Knight

    Dark Knight [OP] Well-Known Member

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    did some more testing after work. this time it seemed not to matter if the vacuum line was connected to the booster or not, the front brakes just wanted to grab/lock up. is it possible for the booster to just be stuck or maybe the spring that makes it equalize pressure is broken, or maybe......:annoyed:

    oh by the way that white in-line valve in the booster vacuum line only lets air go towards the engine, it does not let air pass back to the booster
     
  10. Sep 9, 2009 at 6:44 AM
    #10
    98tacoma27

    98tacoma27 is gooder 'en chicken Moderator

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    5100's all on fours
    That is the way that valve should work. It sounds like the other valve is stuck open. It should only open when the brakes are pressed.
     
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