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A3 2.0TDI BKD, Weird issue with boost/pollen filter!

Discussion in 'A3/S3/Sportback (8P Chassis)' started by SmithyAG, Feb 12, 2014.

  1. SmithyAG
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    SmithyAG Active Member

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    [Feb 12, 2014]
    Hi, The car is a 2004 2.0TDI, BKD engine.


    When the turbo boosts, there is air rushing into the passenger footwell, apparently from the pollen filter housing. At first I thought I was going mad, as that couldn't be possible, but sure enough it only happens when on boost, and varies with boost. Put foot down and the air/sound gets louder and faster, until you let off and it stops.

    The car drives as normal/expected.


    I can't get my head around it, surely the two aren't connected at all? Any suggestions where to start before I start ripping the glovebox out to poke around?


    Thanks

    Smithy
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  3. c_w
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    c_w Well-Known Member

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    [Feb 12, 2014]
    Sounds like a boost leak under the bonnet?
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  4. SmithyAG
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    SmithyAG Active Member

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    [Feb 12, 2014]
    My thoughts exactly, however why/how would the leak get through to the passenger footwell? Unless the boost leak is somehow forcing air into the pollen filter housing from the other side of the bulkhead.

    The car drives fine, and even on prolonged acceleration, there is no error code for underboost, so the leak may be small?
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  5. NHN
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    NHN Retrofitter - Audi - VW - Skoda - Seat Site Sponsor VCDS Map User

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    [Feb 12, 2014]
    Logically, its not possible as the intake system doesn't go anywhere near that area.
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  6. c_w
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    c_w Well-Known Member

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    [Feb 12, 2014]
    You can have massive boost leaks without warning lights (the boost pipe off mine popped off complete; got no warning lights but just had zero power). However with a slight boost leak the car would still drive fine but high pressure air would make enough hissing noise to be audible in the cabin.

    I would guess a pipe from the turbo (which is right at the bulkhead) is leaking??
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  7. SmithyAG
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    SmithyAG Active Member

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    [Feb 12, 2014]
    I know, it's bizarre. The air intake goes around the other side of the engine.

    I can only think that the pollen filter cover is loose and it's letting air escape, and is unrelated to boost/turbo.

    OR I do have a boost leak, which just becomes more audible and sounds like its coming from the footwell.

    I'm inclined to think it's option 1 to be honest, as if I turn the heater fan off, and put my foot down, I can send very cold air into the footwell.
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  8. SAiLO
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    SAiLO Enthusiast VCDS Map User

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    [Feb 12, 2014]
    As you are accelerating more air is being pushed into the car?
    Just a guess but even with the fans off the air keeps coming into the care - more, the faster you drive.
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  9. SmithyAG
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    SmithyAG Active Member

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    [Feb 12, 2014]
    SAiLO, this was my first thought, but it appears directly boost related. For example if i put it in a higher gear and put my foot down, (creating a large boost situation), the air coming into the cabin increases far faster than the car gathers any more speed.
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  10. Boon
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    Boon Active Member VCDS Map User

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    [Feb 12, 2014]
    Maybe a previous owner had or started to put a boost gauge in and a pipe behind the dash without disconnecting it from the intake system??

    Have a look for strange pipes from the intake going into the cabin

    Failing that as said it's coming in from an open vent flap
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  11. SmithyAG
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    SmithyAG Active Member

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    [Feb 12, 2014]
    Pollen filter cover has been put back on nice and tight and it's far less noticeable now.

    Had never thought of a boost gauge line causing it, however it's not the case as the previous owner (from new) was a family member, and she wouldn't know what a boost gauge was, let alone how to install one!

    Thanks for all the comments.
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