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Thread: Hydraboost bleeding question

  1. #1
    Join Date
    Dec 2006
    Location
    Oxford, Ohio 45056
    Posts
    175

    Default Hydraboost bleeding question

    Fred and I have bled the brakes on my Chevy CUCV hydraboost that is in mine m715. We began with the rear brakes and never got any "pedal", the fluid just sorta run out every now and then. We then went to the front and at that point got plenty of pedal. To the back we went again with the same results. I did not bleed the master cylider before starting and now am considering a pressure bleeder.

    Any suggestions other than that ??
    I did buy the master Cylinder used and do not know if it is good, I guess the front (small reservoir) could possibly not be working??

  2. #2

    Default

    EDIT: that page actually sucked. SOrry.


    I've got the Chevy TSM, I'll look through it in a second. I never bled mine, just drove it for a few miles and let it work itself out.

  3. #3

    Default

    Nothing to bleeding the hydraboost unit , done many . You just run the engine at idle , make sure fluid is all the way up , work the pedal and steering ,if it has P.S. This will bleed air out of that system .To check the hydraboost unit , run the engine to pressurize the hydra , turn off engine , pump the pedal , usually 3 to 4 times , you will feel the pedal get hard [just like if you lost vacuum to standard P.B]. Sounds more like your problem is more towards master cylinder as you said . Small resevoir is for the rear shoes.Possible stuck porportioning valve ,maybe still some air stuck in system or weak master cylinder .Also make sure the rears are adjusted up .

  4. #4

    Default

    Sorry,forgot something. If you have rear emergency brakes , could be possible that the cable was adjusted up to engage the EB before the shoes were properly adjusted first . Seen this before ,it causes a low pedal due to wheel cylinders having too much travel .

  5. #5
    Join Date
    Dec 2006
    Location
    Oxford, Ohio 45056
    Posts
    175

    Default

    Quote Originally Posted by fasteddie View Post
    Nothing to bleeding the hydraboost unit , done many . You just run the engine at idle , make sure fluid is all the way up , work the pedal and steering ,if it has P.S. This will bleed air out of that system .To check the hydraboost unit , run the engine to pressurize the hydra , turn off engine , pump the pedal , usually 3 to 4 times , you will feel the pedal get hard [just like if you lost vacuum to standard P.B]. Sounds more like your problem is more towards master cylinder as you said . Small resevoir is for the rear shoes.Possible stuck porportioning valve ,maybe still some air stuck in system or weak master cylinder .Also make sure the rears are adjusted up .

    Thanks for info.

    I forgot to add that the motor is not running yet. I assume I will need to start before I can determine if the MC is any good ??

    Or will a pressure bleeder do the trick ??

  6. #6
    Join Date
    Dec 2003
    Location
    Giddings, Texas
    Posts
    7,729

    Default

    Think of it as two separate systems. The mechanical/hyraulic brake system and the booster system. The brake system works just like any other non boosted system. Get the air out and don't have any leaks.

    The Hydroboost booster system needs pressure from the power steering pump to energize. You won't know if it works until you get the engine running. Picking the front end up and turning the steering wheel from lock to lock helps get all the air out. Just have the tank cap off when you do it so you can watch for low fluid and bubbles. The bubbles indicate air. If it looks like a draft beer, shut the engine off and give it time to go back to fluid.
    Remember if you didn't build it you can't call it yours.

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