brake bleeding problem

Discussion in 'The whoa and the sway.' started by Tom Gwillim, Sep 20, 2004.

  1. Tom Gwillim

    Tom Gwillim Active Member

    Well heres the problem. I haven't done much work to my car lately but I bought a new master cylinder from Auto Zone to finish my disc brake conversion on my 70 GS. Everythig is new except the booster, calipers, and prop valve. The prop valve is the 71-72 style. I bench bled the master cylinder with no probllems. I installed it on the car and the fluid will not go out of the master cylinder when I push the pedal. I took the cover off the master cylinder and it does nothing when I push the brake pedal. I adjusted the rod on the booster and it appears to move out about 1 1/4" when you depress the brake pedal. Is there a difference between the drum brake and disc brake booster or is ther sometihing else that I am missing?


    Tom Gwillim
    Swartz Creek, MI
  2. GStage1

    GStage1 Always looking for parts!

    Get your self the might vac (one-man) system. They work great. Also, make sure you installed new rubber hoses. Open a bleeder and connect the might-vac and it will draw a lot of air and is much quicker than the old pump and realease bleeder method.
  3. sailbrd

    sailbrd Well-Known Member

    Hi Tom,
    Still have not had a chance to come over and see your project, have had a busy summer. On your brakes you say it bench bled properly so that means that it has to be trying to move fluid. I have a brake testing kit and mighty vac. We could just plug that into the booster and check for pressure. Let me know if that would help and I could come over and give you a hand.
  4. gstewart

    gstewart Well-Known Member

    have u considered using a pressure bleeder instead of a vacuum bleeder ? these gm disk brake systems can be real buggers to bleed properly .
    what i would do would be to open up all the bleeders a full turn or two , and see if any of the brake fluid will drain through the lines to remove excess air . the shop manual advises that method .
  5. Tom Gwillim

    Tom Gwillim Active Member

    I looked at it a little last night. It still seems that the brake pedal is not pushing the piston on the master cylinder. I'll try to gravity bleed this weekend and see what happens. Doug if I get in a jam I'll probably take you up on your offer. Its been a busy summer for me also and I haven't accomplished much on the car. Sounds like you have your car rockin!


    Tom Gwillim
    Swartz Creek, MI

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