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Help - rear abs sensor removal s4

Discussion in 'A4/S4 forum(B5 Chassis)' started by sun and kath, Jan 10, 2009.

  1. sun and kath
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    sun and kath Member

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    [Jan 10, 2009]
    Stripping rear suspension, going to fit new disks/ pads, spring and bushes and bearings.
    Need to get the upright off to do the bearing.
    After 3 hours (sure the otherside will be quicker, now i know what to do)
    I have the upright off apart from the abs sensor!!!
    The 5mm allen key bold that holds it snapped, tried tapping sensor with hammer and it will not buge. Have broken the bit off the sensor where the little bolt goes to hold it on.
    How am i meant to get this off?
    Do i just assume its sized and smash it , then buy a new one.
    Where are the electical connections, will i have to disconnect it in the enginebay?

    Any tips?

    [​IMG]
    #1
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  3. dieselfitter251
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    dieselfitter251 Blow ma own trumpet?

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    [Jan 10, 2009]
    Don't know, that's different to my set-up, I'm all over the ABS sensors on my quattro, I thought they'd be the same as yours. However, when I first opened my can of ABS worms three of my sensors were corroded in, had to be dug out from inside the hub. The metal cap of the sensor that inserts into the hub on my car houses the electronic gubbins, (magnety type bits) had to be knocked back from the inside, a new copper retaining sleeve had to be bought. After about 10mins of gouging it was aparant that new sensors were required too.

    Sorry it's not much help, but I expect that if a sensor is jammed in you have the same outcome.
    #2
  4. andybnwc
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    andybnwc Member

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    [Jan 10, 2009]
    I suppose im gonna have to do this too , my nearside rear is siezed . I will be keeping an eye on this thread , also why are the rear sensors so much money?
    #3
  5. dieselfitter251
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    dieselfitter251 Blow ma own trumpet?

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    [Jan 10, 2009]
    I've no Idea why, I've tried to ask Audi techs why they're different, GSF & Sales people why they're OEM only etc..and no real answer, (other than the patent hasn't been released). I've checked out sites in the US and it looks as though they can get after market parts out there but not here, go figure eh?

    Also, you'd think it'd just be the same set up as the front sensors with there being drive shafts and stuff.... I'm half tempted to get a front sensor, whack it in and see what happens though I'm guessing it's something to do with impedance so it won't work, or maybe the EDL function? Again, why the hell are they so much more money! and I need two! and maybe a new module!!!

    Any techies around to answer this?
    #4
  6. Siena
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    Siena Active Member

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    [Jan 11, 2009]
    When replacing wheel bearings on the rear, I leave the sensor in place.

    I simply remove the rear seat squab, unplug the sensor, push out all the grommets, then feed the coaxials out.

    It's the easiest way, that way nothing's disturbed.

    Dieselfitter, how much were you quoted for sensors?
    #5
  7. sun and kath
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    sun and kath Member

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    [Jan 11, 2009]
    Thanks for the comments
    I now leave te sensor in place on the other side.
    Only worry is i may have damaged this one by "moderately" tapping it with the hammer. Is there anyway i can test it with VAGCOM with the car stationary? Obviously don't want to reassemble the rear suspension, if i then have to strip it to drill out the abs sensor.
    #6
  8. Siena
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    Siena Active Member

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    [Jan 11, 2009]
    I doubt you could VAG-COM it the way it is.

    You could however, take resistance readings from it, and compare with the side you haven't hammered.

    There are no moving parts within the sensor - it's just a coil / magnet, operating on the Hall-effect principle, so unless you've destroyed the tip that reads the rotors on the CV joints, they'll be ok.
    #7
  9. sun and kath
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    sun and kath Member

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    [Jan 11, 2009]
    thanks for the explaination that the sensor is a simple unit - gave me hope.
    So i have placed the drive shaft back into the hub in the suspension upright . then put vagcom to the car. I am not expert in this but have previous found it an excelent product.
    within the abs module i got no fault codes.
    so then when to measuring blocks from within the abs module and found 3 measuring block oprtons gave data, i think it was the first one that appears to give 4 wheel speed readings. so i clicked on the graph option (can't recal its name) and rotated the other back wheel (that i had not messed with) and sure enough there where readings on the graph.
    Then when to the side i had dismantled and rotated the hub
    a graph reading was produced similar to the good side.Fantastic!!

    Obviously no road test but given this i will press on and not replace the sendor.
    Found the conections as well, right under the seat ( to leave the sensor on the arm) so back to making progress tonight
    thanks guys
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  10. Siena
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    Siena Active Member

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    [Jan 11, 2009]
    No worries, good luck geting her back together.
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  11. SonicDeathmonkey
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    SonicDeathmonkey Member

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    [Jan 11, 2009]
    Given that my VAGCOM has started throwing rear abs sensor errors, what are the costs involved in replacement?
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  12. Siena
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    Siena Active Member

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    [Jan 11, 2009]
    ^^^ I'll PM you.
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  13. dieselfitter251
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    dieselfitter251 Blow ma own trumpet?

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    [Jan 11, 2009]
    I can't remember now Siena, I was going to call but I had 7 loads of washing to do, iron. Hoovering. Kitchen floor to clean and prepare for house guests :O) ....ain't I the little house-wife:)...

    I think the last quote I got was £120+ ... not sure tbh. I just went for used ones the last time, 2 for £70. Didn't do much good though. Could you PM me a price? Cheers
    #12
  14. Siena
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    Siena Active Member

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    [Jan 11, 2009]
    ^^^ No worries, Diesel.

    Will do so tomorrow.
    #13
  15. jcb
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    jcb Active Member VCDS Map User

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    [Jan 11, 2009]
    won't the fault code only be generated when brakes applied and readings are taken?
    #14
  16. SonicDeathmonkey
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    SonicDeathmonkey Member

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    [Jan 11, 2009]
    £120 for each sensor? How much labour (hours) can I expect to pay to get one changed?
    #15
  17. Siena
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    Siena Active Member

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    [Jan 11, 2009]
    SDM, labour shouldn't be more than 30 minutes per side.
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  18. SonicDeathmonkey
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    SonicDeathmonkey Member

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    [Jan 11, 2009]
    ^^^ sweet. I guess I just need to make sure the garage know what they are doing then. It's not going to pass the MOT with the sensor up the spout!
    #17

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