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brake problem help please

Discussion in 'Chevy Trucks' started by TTBoy77, Jan 30, 2007.

  1. TTBoy77

    TTBoy77 Member
    Messages: 87

    I have an 86 chev 3/4 ton, 350, 7' 6" western pro, and I am having a brake problem. The brake light keeps coming on and I don't know why. The truck is not using any fluid so that eliminates a leak. Shy of bleeding the brakes, could there be an issue with the vacuum? The front does need new pads and maybe even rotors (not sure 'bout the rear).:( Also when I step on the pedal the is a clicking coming from inside the cab which I attributed to the brake light switch...sound right??
  2. ahoron

    ahoron Senior Member
    from here
    Messages: 422

    Master cylinder?
  3. BOSS550

    BOSS550 Senior Member
    Messages: 212

    brake problem

    Sounds like a master cyl. How's the pedal feel? Probably not vacuum cuz you would have a hard time keeping the truck running with a hole that big leaking off.
  4. TTBoy77

    TTBoy77 Member
    Messages: 87

    how exactly can you determine it's the master or the booster for that matter? Is that a salvage yard part or something that should be purchased new? I don't think bleeding the brakes will help 'cause it doesn't seem like there is air in the lines..i.e. not a "good pedal sometimes and not a good one other times". Is that some sort of valve or breather that the big line from the booster goes to?
  5. BOSS550

    BOSS550 Senior Member
    Messages: 212

    chevy brakes

    Is the pedal firm or soft? Does it go all the way to the Floor? If it ain't leaking fluid anywhere then it ain't got air in the lines. If you answer soft to the first question or yes to the second replace the master. If the booster is bad you will hardly be able to push the pedal at all with the truck RUNNING. In all my years driving and racing chevy trucks I've never seen a booster go bad. All it is is a huge diaphram that when the motor is running is uses engine vacuum to help you move the plunger in the master cyl. You push on one side while the boosters pulls. This gives you power brakes. I would start with the master and make sure you bench bleed it before you install it. May be a good idea to start soaking the caliper and and wheel cyl bleeders with PB Blaster a while.
  6. TTBoy77

    TTBoy77 Member
    Messages: 87

    thanks for the help...i'll try that first 'cause the pedal is soft
  7. Mark Witcher

    Mark Witcher Senior Member
    Messages: 604

    The warning light is connected to the proportioning valve. The valve senses when there is uneven fluid movement between the 2 brake systems. If your pads are wornout, replace them first and then the master.
  8. sweetk30

    sweetk30 PlowSite.com Addict
    Messages: 1,588

    yes its on the prop valve. but aslo tyed in to the ebrake pedel. check the pedel to see if its up all the way. if the cables are stuff and dont alow the pedel to be pulled back 100% it can trip the switch for the light. but i would swap out some pads first and if you havnt done a fluid flush in a bit 2-3 years blead the brakes all 4 to get old fluid out and any moisture in the system out.

    moisture in a brake system thats worked hard will turn to steam and create air pockets. also the old fluid will make the pedel spongy. i had a 4 wheeler one time that had the origanal fluid in the disk brakes and it was o.k. no air. but i flushed it and wow what a big diffrence in the feel of the brakes.