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S2 coupe brake pedal going soft / collapsing on track

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  • S2 coupe brake pedal going soft / collapsing on track

    I noticed last year while I had my S2 on the track at Bedford autodrome that after a couple of laps the brake pedal was collapsing and moving further down then it's normal firm position. I'm running AP racing DOT 5.1 brake fluid with 6 pot Porsche cayenne turbo S calipers with 370mm discs and boxter calipers on the rear with 300mm discs.

    I want to solve the issue but do the right thing.....what do you guys think it could be ?

    The hydraulic bomb setup not being able to cope?

    power steering fluid getting hot causing the above?

    or something else, I was considering upgrading to the double booster vaccum setup but not sure if it would solve the issue

    Thanks

  • #2
    What brake pads are you using? Did you fully bleed the system of air?
    91 Modded 3B
    14 A6 Avant Black Edition

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    • #3
      Brembo Fast Road....haven't made it to DS's yet.....yes system was fully blead properly.....its a street legal car so I drove it quite a bit and brakes were fine

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      • #4
        Upgrading to vac would be a good idea. The bomb only holds pressure to aid braking assistance when the engine/hydraulic pump is off. It shouldn't affect normal driving unless it's completely gone. I think you may feel pulsing on peddle depression if the bomb is doing nothing. Leaking master cylinder?
        91 Modded 3B
        14 A6 Avant Black Edition

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        • #5
          I overheated my PAS fluid on a track day. Steering was heavy and noisy, but the brakes were unaffected.
          91 Modded 3B
          14 A6 Avant Black Edition

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          • #6
            No leaks on master....could the brake fluid have reached its limit ?

            I do remember the pedal pulsating....after a cool down the brakes were fine on the way home.

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            • #7
              Air or boiled the fluid i think
              sigpic

              1992 3b S2 Coupe

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              • #8
                PAS and brake circuits are completey separate. Upgraded booster wont solve this problem. The issue is heat - from what you describe, most likely you smoked your pads. If you boiled your fluid and vapour locked the brake hydraulics, the spongey pedal would be permenant until you bleed your hydraulics, i.e. the drive home would be equally perilous - try some DS2500 or equivalent road legal track day pad compound.
                Panthero Coupé quattro 20vt
                Indigo ABY coupé
                Imola B6 S4 Avant

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                • #9
                  Thanks Alex....i'll give it ago

                  Thanks Guys for your help

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