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A4 brake failure

Discussion in 'A4/S4 forum(B5 Chassis)' started by dontknow17, Apr 4, 2011.

  1. dontknow17
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    dontknow17 New Member

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    [Apr 4, 2011]
    hi all,

    my A4 1.8t avant 1997 wont stop! the brakes only work when you stand on the pedal and only works a couple of inches from the floor. it did it a few days ago but then cured itself within minutes. anyone have any ideas as to what it could be? im completely comfused!

    cheers
    Elliott
    #1
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  3. dontknow17
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    dontknow17 New Member

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    [Apr 4, 2011]
    oh and it wont cure itself this time, ive tried pumping the pedal (like last time) and no joy this time!
    #2
  4. ScottD3
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    ScottD3 I want your faulty electronics

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    [Apr 4, 2011]
    How is your brake servo?
    I've read that they rust out at the bottom because the drain holes get blocked, that area fills up with water and rust out the bottom of the brake servo. which then causes the brakes to fail.

    Just an idea for something for you to check.
    #3
  5. Oranoco
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    Oranoco Well-Known Member

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    [Apr 5, 2011]
    Is the pedal very soft. Sound rather like the brake master cylinder. If the servo failed I would expect a very hard pedal.
    #4
  6. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator VCDS Map User

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    [Apr 5, 2011]
    yeh or a leak/burst hose somewhere.
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  7. dontknow17
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    dontknow17 New Member

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    [Apr 5, 2011]
    it does pull to the right when you brake as hard as possible, the pedal had no feel for the first 4/5 inches then its rock hard at the bottom. there is a hissing sound when you push the pedal down, ive had a look at the servo and cant see any massive problems. is there a possibility that the previous owner put pas stop leak in the brake fluid by mistake which could cause this. he admitted to it when i picked the car up but i thought nothing of it.
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  8. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator VCDS Map User

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    [Apr 5, 2011]
    As i've said, your losing fluid somewhere. You've probably lost one of the two braking circuits.

    If you dont know what your doing, please dont mess around and take the car to a garage immediately to have it fixed before you kill someone
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  9. glazeautoparts
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    glazeautoparts New Member

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    [May 23, 2012]
    hi there

    it sounds like the servo has gone they are normally between £350-£700 from the main dealers but we have sorted out some aftermarket ones for £145+vat

    many thanks glaze auto parts
    #8
  10. Ste_Nova
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    Ste_Nova Active Member

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    [May 23, 2012]
    i had failed master cylinder on my passat fluid was getting back past the seals, leaving me with a soft pedal and **** brakes,

    with the car switched off, pump the pedal a few times to use all up the servo help, then stand on the pedal firmly, it should come to a firm stop and shouldn't sink at all , sinkage = fluid moving where it shouldn't
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  11. boost-addict
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    boost-addict Member

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    [May 25, 2012]
    you mean pump the brake till its hard, then start the car. if it sinks then you have problems.

    sounds like seals or the servo.
    but could easily be the brake unit its self. just get it towed to ats or a garage and get it looked at
    #10
  12. Ste_Nova
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    Ste_Nova Active Member

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    [May 25, 2012]
    no, starting the car then it sinks confirms the servo is working

    i'm talking about using up all the servo assistance then putting pressure on the hydraulic system and seeing if it can hold it or if the pressure is lost, either though leaks of fluid or fluid getting past the pressured section and back into the brake fluid bottle
    #11

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