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Cooked brakes, now pedal makes new noise

Discussion in 'A3/S3 Forum (8L Chassis)' started by DragonHawk, Apr 11, 2009.

  1. DragonHawk
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    DragonHawk Fanatic

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    I made the noob mistake today of letting a couple of people test-drive my S3 without cooling off in between.

    Result: boiled fluid.

    At least that's what I believe happened. After the session I let the engine run for about 5 min to cool everything down (stationary tho), and when I moved the car the brake pedal went straight to the floor, no braking at all! VAG-COM didn't seem to happy about the situation either...

    After a few hours of standing, brakes seemed ok again, except for a little more travel, BUT: now my brake pedal makes a wooshing sound (maybe more of a "pfft") when I step on it. A fellow S3 owner says his does that all the time, so I just thought I'd find out how common this is and whether I should be worried about it?

    Second question: What are the warning signs that you're about to lose your brakes to boiled fluid? Kinda scary to just suddenly have no brakes at all!

    Third question: Is it safe to drive a few days/weeks with fluid that's been boiled, or does the boiling leave the fluid unsafe? I do intend to replace the fluid asap, but would be nice if I can delay until I make my mind up about brake upgrades etc...
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  2. DragonHawk
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    Bump

    Anyone at least have a response regarding the noise from the pedal? Is this common/normal?
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  3. Dennis Moeller
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    Dennis Moeller Member

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    My brake pedal makes no noise...except from the obvious sound that comes from every brake pedal if pushed suddenly and firmly..
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  4. HTC
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    HTC Active Member

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    My brake pedal makes that noise. Always has done.
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  5. DragonHawk
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    Cool, thanks for the replies!

    Bit strange that only some of them seem to do that and that mine suddenly started doing it (unless I just never noticed it before :shrug:). But at least now I know of two other people with the same "symptom" so I don't need to lose sleep over it :).

    Still curious about the cause tho, so might take a closer look sometime...
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  6. DragonHawk
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    To answer some of my own questions for the benefit of other readers, check the following link:
    http://www.stoptech.com/tech_info/wp_warped_brakedisk.shtml#

    Myth #4 - Warns that fluid needs to be bled off after boiling. Of course the degree of degradation probably depends on many factors so results may vary...

    Myth #3 part B - States that you'll have ample warning before boiling fluid sends you into a ditch/tree. I can't vouch for this from my own experience, but I can add the following very important warning: While you may have warning of impending brake-loss while driving, there might be NO warning before you COMPLETELY lose your brakes if the car has been stationary for a while after cooking the brakes! This could happen if heat builds up (no airflow while car is stationary) and the fluid has time to boil properly before you move off again.

    At least the whole experience has educated me a bit plus it alerted me to the fact that I've got rusty water for brake fluid at the moment :puke: (have only had the car for a week).
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  7. DragonHawk
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    I've been thinking about the noise from the pedal. The only moving (compressing) part I know of down there that has any air in it is the rubber boot around the rod from the pedal to the master cylinder.

    I suspect that when my pedal first went to the floor it damaged the boot and the sound I hear when I depress the pedal is air being pushed out of the boot as it's compressed. That would explain why some cars make the sound and others don't.

    Haven't tested my theory yet; will post here when I've checked it out...
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