No brake pressure - Help!

Discussion in 'Chassis' started by Bomber604, Jun 29, 2020 at 9:15 PM.

  1. Bomber604

    Bomber604 Forum Member

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    Jul 10, 2009
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    Location:
    Shrewsbury
    As some of you may know, I'm getting towards finishing my MK2 ABF race car.

    I thought I'd finished the braking system this evening but no! After persuading the wife to sit in the car & operate the brake pedal for me (a feat in itself) all the calipers appeared to bleed fine, nice clear fluid, no bubbles. Only after I locked off the final bleed nipple my good lady informed me that the brake pedal was still going all the way to the floor with little resistance.
    There is no evidence of a leak anywhere so why no pedal?

    System Spec:
    G60 front calipers
    Standard GTi rear discs & calipers
    New copper lines throughout
    Bias valve by gearstick (fully open)
    Load compensation valve removed
    9" Servo
    New 22mm alloy master cylinder
    Dot 5.1 fluid

    Any thoughts on what could be wrong?

    TIA
     
  2. Savagesam

    Savagesam Moderator Moderator

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    Is the servo new? Seen this quite a bit recently and it been a knackered servo
     
  3. Bomber604

    Bomber604 Forum Member

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    Yes, brand new. I'm not discounting it as the cause of the issue though.
    There's always the possibility I missed something when fitting it.
     
  4. Tristan Forum Junkie

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    Fluid trapped in the rear calipers. This comes up at least once a month on average. I never would have believed it until I got caught out by it myself years ago.
     
  5. Bomber604

    Bomber604 Forum Member

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    & how do I fix that?
     
  6. Tristan Forum Junkie

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    https://www.clubgti.com/forums/index.php?threads/spongey-mk2-brakes-aargh.242352/

    Search engine is your friend.

    I usually keep the pistons locked with a caliper windback tool. And hold the calipers as high as the flexible pipe allows, bleed screw pointing up and the highest point. And a few taps of a spanner while bleeding.

    This method has restored good brakes on at least 4 cars that others gave up on.
     
    Simon Peter Dodgson likes this.

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