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air leak when pressing the brake pedal

Discussion in 'A3/S3 Forum (8L Chassis)' started by m8arx, Mar 10, 2012.

  1. m8arx

    m8arx Member

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    Hi guys,

    My car alarm was going off non stop and the mrs couldn't stop it while i was away so because of that, the battery died and subsequently the car sat for 2 weeks with no power. I jump started it when i got back and all was ok, apart from the brakes.

    I think the above is a red herring because i don;t think a flat battery could cause this.

    Basically, when i brake, there is a hissing noise coming from around where the brake pedal is in the car, and the brakes don't really feel spot on. I've read on the forums about brake servo's, vacuum hoses etc, but i'm not really sure which one to look for as different people have had different experiences.

    Basically, the hissing noise only happens when i'm pressing the brake pedal, for the first half a second or so. If i pump the pedal, it does it everytime for the first half second on each pump. it does NOT hiss when the brake pedal is not being used.

    Brakes are obviously a biggie on cars and i don't want to mess around with something unless i know what it is for definate. The garage that does all my work doesn't seem to think it's an issue however i do as the brakes don't stop me as well as they used to (standard brakes btw).

    Anyone got any suggestions as to whether it could be a hose, and if so which hose/where is it?

    Cheers

    Mark
     
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  3. Alais DJA

    Alais DJA Member

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    Brake piston valve - had a mk2 golf that did the same thing....could possibly be the same
     
  4. aragorn

    aragorn "Stick a V8 in it!"
    Staff Member Moderator VCDS Map User

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    I'm sure most cars will hiss slightly when you press the brake due to the servo. You cant normally hear it with the engine running etc though.
     
  5. S3featesV9

    S3featesV9 Active Member

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    Mine does the same thing. Always has. Could check vacuum pipes to the servo. I replaced these but it still isn't any better. Think it may be normal?
     
  6. m8arx

    m8arx Member

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    I can definately hear it when the engine is running and i'm driving. Like i say i've never heard it doing it before so wondering if it could be a vacuum hose or something?
     
  7. Alex C

    Alex C Well-Known Member
    VCDS Map User Audi S3

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    does your brake pedal feel harder?
     
  8. m8arx

    m8arx Member

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    No the brake pedal feels a lot softer
     
  9. A3 T

    A3 T Lord Of The Rings

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    I had the same sort of problem ages ago and made a thread:


    http://www.audi-sport.net/vb/a3-s3-forum-8l-chassis/114807-not-my-day-today-hissing-brake-pedal-now.html#post1194807


    I bought a new servo but then found out i was a right pain in the a*s to change. Then i found out on another forum that if you spry some silicone grease down the inside of the gaiter with the engine running and the same time as you pump the brake pedal it can fix it.


    A week now and its still going strong (famous last words...lol).
     
  10. m8arx

    m8arx Member

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    Cheers a3t, but you seem to have a hissing sound when you're not pressing the brake and it stops when you press it if i'm reading your thread correct? Where did you spray the silicon grease into and who told you to do this?
     
  11. A3 T

    A3 T Lord Of The Rings

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    Yeah but i figured it must be the same seal making the noise.....lol


    I read it a while ago but i think it was this thread:


    http://www.vwt4forum.co.uk/showthread.php?t=6541
     
  12. James333

    James333 Member

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    I have the same issue, if you look at ELSA, it seems it is an expected problem as the remedy has its own section....


    If it is anything like mine, there is a suction type woosh noise when you press the brake, I think it does it with the engine off too. I am fairly sure it is not a vacuum leak because if I switch the engine off and wait 5 minutes, when I apply the brake, it is still servo assisted suggesting there is no leak in the system as it's holding the vacuum. I came across the fix by accident but basically it says. The drivers side luggage compartment needs to be removed and there is a rubber boot (very similar looking to a CV boot) that fits over the push rod going into the servo from the pedal, when this comes off, you get the noise. Re fitting this should solve the issue :)

    I'll get on elsa now and see if I can paste the page on here!
     
  13. James333

    James333 Member

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    [​IMG]

    [​IMG]
     
  14. James333

    James333 Member

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    [​IMG]

    These may help? The problem on mine is caused by the bellow numbered 20 in the first picture.
     

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