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rear brake problem driving me nuts!!

Discussion in 'A4/S4 forum(B5 Chassis)' started by jcb, Jul 16, 2010.

  1. jcb
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    jcb Active Member VCDS Map User

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    [Jul 16, 2010]
    recently replaced some brake lines and in the process of bleeding them I realised they were binding (or to be precise were well and truly bound!).
    finally managed to get a stupid wind back tool online (which is made of chocolate and is fecked already!) but as I bolloxed up finding the thread on one piston I managed to pull it out and needed to re-bleed them.

    So pistons wound in, pads and discs refitted, lots of clearance, sliders, pads and calipers all move around no probelm and I re-bleed.

    binding.
    badly!

    what the f@$% is happening here!

    exact same brakes and pads that came off going back on. nothing changed other than a bleed.

    something I am missing here?
    #1
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  3. hiltoa
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    hiltoa VAG erfahren

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    [Jul 16, 2010]
    Could be an internally damaged flexi hose, letting fluid into the caliper, but stopping it from draining back.
    #2
  4. jcb
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    jcb Active Member VCDS Map User

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    [Jul 16, 2010]
    no flexi hoses on my car!
    all new stainless braided, dont see any damaged ones, but I supposed there could be a crimp, but surely it would leak away after some time?
    #3
  5. Jonion
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    Jonion Member

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    [Jul 16, 2010]
    Still a sticking piston or slider pins I'd say.

    What about the handbrake and it's mechanism?
    #4
  6. jcb
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    jcb Active Member VCDS Map User

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    [Jul 16, 2010]
    sliders are not sticking, easily pull out with finger and thumb.
    Handbrake is tight but the spring is fully open som it is not on.
    before I bled it the caliper could be slid back and forth in the gap that the piston rewind had created, hand brake hasn't been applied since then so I ruled that out.

    when I was bleeding them I had to get the pedal man to pump a lot of air out since I had opened the piston up, once it came through without air the pedal firmed right up.
    I closed off the nipple with the pedal down to avoid air being sucked back in as I alwasy have done, just this time it doesn't release for some reason. bled them with the ignition off the first time and with it running the next time.

    no idea what it can be
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  7. Jonion
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    Jonion Member

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    [Jul 16, 2010]
    curious...
    I always lock off the bleed nipple with pedal down, how it should be done.
    No need to have engine running though.
    Have you bled the rest of the system recently? I'd do that anyway as a matter of course.
    But if only one caliper sticking then the problem must lie in the pipe to that caliper or the caliper itself. It's possible it's further up in the ABS unit/controller, master cylinder but very unlikely.
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  8. jcb
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    jcb Active Member VCDS Map User

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    [Jul 16, 2010]
    I am going to strip it all down again tomorrow but it is really pissing me off now, can has been off the road nearly over a month with various cock ups tools missing or parts on order!!
    #7
  9. ian52
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    ian52 2000 a4 1.8tqs-yellow

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    [Jul 16, 2010]
    Does seem like a strange one.
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  10. adamss24
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    adamss24 Well-Known Member

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    [Jul 16, 2010]
    JCB, did you bleed before you pulled the handbrake or after ? There might be dammage to the worm screw but i would rewind them fully then push the brake then adjust the handbrake.
    #9
  11. jcb
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    jcb Active Member VCDS Map User

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    [Jul 16, 2010]
    havent had a chance to touch the handbrake, just reconnected it
    #10
  12. jcb
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    jcb Active Member VCDS Map User

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    [Jul 20, 2010]
    sorted it!

    stupid thing really, there is a slight casting difference between the rear uprights from the 1.8tqs ones to the ones I bought from Docurley, that meant the rear lower "leg" that the rear tie rod bolts too is slightly fatter with a defined casting ridge that fouled the 90 deg bend of my goodridge motorsport braided brake hoses.

    as soon as you put the brakes on it held them in place.
    quick squiz with a tungsten carbide bit and it cleared the casting right up.

    Back on the road.....finally, only been 6 weeks!!

    cheers for the suggestions anyway
    #11
  13. Jonion
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    Jonion Member

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    [Jul 20, 2010]
    Wow, you shoudl patent that design.
    Self-holding rear brake. For those unsure if they want to release the handbrake.

    Glad you got it sorted .
    #12

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