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Soft brake pedal.

Discussion in 'T3 & T4 Tech Help Clinic' started by beerboy, May 26, 2018.

  1. beerboy

    beerboy Well-Known Member

    Messages:
    1,047
    Location:
    Sydney
    I have replaced my whole braking system. new master lines the lot. The pedal is good when engine off. But when running the brake pedal goes to the floor. Bit stumped no sure if I havent bleed all the air out properly or if the booster / vacuum side is bad. help appriciated. I thought adjusting the rears had it fixed but started van and brake pedal to floor again
     
  2. BackintheDak

    BackintheDak Member

    Messages:
    52
    Location:
    Tasmania
    Sounds really strange that you get pedal when not running but none when running? Is the Master cylinder identical, maybe it has different internal dimensions, really not sure what you are up against. Have you checked the one way valve on the booster suction?
     
  3. beerboy

    beerboy Well-Known Member

    Messages:
    1,047
    Location:
    Sydney
    I have a strange feeling I havent bleed the brakes properly. bleeding with engine running could be the fix
     
  4. BackintheDak

    BackintheDak Member

    Messages:
    52
    Location:
    Tasmania
    When you installed the master cylinder did you bleed it? used to have to do so when I was playing with Mazda Rotary's many many years ago. Also when you bleed the brakes are you starting at the furthest from the master cyl?
     
  5. Dapom

    Dapom Well-Known Member

    Messages:
    805
    Location:
    Brisbane
    If there’s no air bubbles when you bleed then you should be good there. I’ve just completed my brake rebuild and rear drum adjustment is key. Loosen handbrake cables right off so there’s no tension then adjust rears till they bind....stand on the brakes a few times. Check the adjustment and keep going till they stay in the binding position. I then adjusted up handbrake so it was hard on at 3 clicks and then stood on the brakes hard a few times with handbrake on. I heard the adjusters twanging about on the rear drums and hey presto I had a good pedal.....solid at same level as gas pedal with engine off. With engine started pedal is lower but brakes are good so gonna drive and settle them in a bit then adjust again.
     

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