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Thread: Master cylinder?

  1. #1
    Registered User LIRS6's Avatar
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    Master cylinder?

    Mushy brake pedal, basically goes straight to the floor. Developed fairly rapidly. I can pump the pressure back up, but then it dissipates quickly again. Checked fluid level - it's fine. Am I likely looking at a bad master cylinder? Any other thoughts? Anything I can check myself?

    TIA
    GBNF: Mugello, silver, carbon, RNS-E, H&R coilovers, Hotchkiss
    '14 GL550
    '79 911SC Targa

  2. #2
    Registered User mdegracia's Avatar
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    Parking brake cable corroded and keeping caliper stuck? Or a seized caliper. Master cylinders rarely go bad.
    03 RS6 Daytona Grey - EFI Express - 01e - SRM K24 - Aquamist - 495whp/580ft-lbs

  3. #3
    Registered User hahnmgh63's Avatar
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    Mileage? They can go bad an aren't cheap. It's important to flush your fluid every couple of years, dirty fluid can prematurely wear the Master Cylinder. Always try to pressure bleed rather than the old method of pumping the pedal with someone at the bleeder. On an old cylinder you run the piston past it's normal operating limits by doing this and the old piston usually has some pitting/oxidation on it and it wears the seals like runnning sandpaper over them.
    2003 White RS6 2013 Midnight Blue S5
    2013 Daytona RS5 2x944 Turbo's 1974 911 w/'91 3.6ltr motor
    Roy, WA

  4. #4
    Registered User LIRS6's Avatar
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    Master cylinder it is. After it is repaired, the beast will go on the block. After 147k thrilling miles, I'm ready for a change.
    GBNF: Mugello, silver, carbon, RNS-E, H&R coilovers, Hotchkiss
    '14 GL550
    '79 911SC Targa

  5. #5
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    That's a lot of good miles. Curious as to what you are going to replace the beast with?

  6. #6
    Registered User LIRS6's Avatar
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    Quote Originally Posted by 905084 View Post
    That's a lot of good miles. Curious as to what you are going to replace the beast with?
    GL550 is my intention
    GBNF: Mugello, silver, carbon, RNS-E, H&R coilovers, Hotchkiss
    '14 GL550
    '79 911SC Targa

  7. #7
    Registered User LIRS6's Avatar
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    I asked dealer to place the dead master cylinder in the trunk - he said there may be a "core charge" - has ANYONE heard of such a thing for a master cylinder?
    GBNF: Mugello, silver, carbon, RNS-E, H&R coilovers, Hotchkiss
    '14 GL550
    '79 911SC Targa

  8. #8
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    Very common for a lot of parts. If the part was new there shouldn't be a core charge as they didn't sell you a rebuilt one.

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