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84 Chevy Brake problem

Discussion in 'Truck & Equipment Repair' started by raptorman03, Feb 16, 2006.

  1. raptorman03

    raptorman03 Senior Member
    Messages: 333

    :help: we have a 84 1 ton Chevy and the brakes all of a sudden got no pedal when in Drive, but when its in park it has good pedal. You can even feel the pedal sink down a bit when switching in to drive. What the heck would Cause this?:confused: :dizzy: All we did is replace 1 back rear brake cylinder and put new pads on the fount it worked good for about 3 days and then i jumped in it and all most went through the shop.
  2. KingDuramax

    KingDuramax Senior Member
    Messages: 226

    Sounds like you could have air in the line.
  3. douglasl330

    douglasl330 Senior Member
    Messages: 356

    check the connection from intake to vacuume can behind the master cylender--quite possible that it got tweaked and it is leaking vac. Been way too long since working on older chevy! Hope this helps!
  4. NJBuickRacer

    NJBuickRacer Member
    Messages: 59

    If the brakes were good, then suddenly went bad I'd look towards a hydraulic failure(master cylinder), and check the rear wheel cylinder that you put on. It may have come loose, and when you put the truck in gear it loads the shoes against the cylinder in a way which allows it to contact the shoe better. Check the front caliper attaching points as well, since loose/missing hardware there could also cause the problems you describe.
  5. raptorman03

    raptorman03 Senior Member
    Messages: 333

    Well we bled them again and found a littel bit of air but still had the same problem. But latter today he started it and it was fine ?
  6. NJBuickRacer

    NJBuickRacer Member
    Messages: 59

    If it's intermittent, I'd say the master cylinder is the most likely culprit.
  7. Acmemechanic

    Acmemechanic Senior Member
    Messages: 137

    Pedal fade

    I would most definitely agree as long as you have no leaks in the system.Also unbolt the master and check the plunger at rear.