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Hello all,

Has or does anyone experience a plastic sounding knocking/rattle when accelerating?

It sounds as though it is coming from behind the dashboard and has grown in intensity recently. It doesn't sounds mechanical or from the engine area and my initial thoughts were a loose connection around the air vents, but I can't place the exact source of the sound.

Has anyone found a solution to this, before I head to a mechanic? I am hoping that there is a DIY fix that may be possible.

TIA.
 

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2007 3.2 VR6 Quattro Roadster
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I'd start with looking at the HVAC blower as they can make some interesting noises when the bearings start to go. Good post here to help -
 

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If your car has the "noise pipe" that could be the source of it because that pipe is designed to "pipe in" engine noise to the firewall. It's really stupid IMO, you can delete it (if you have it) by using the parts from a car without the noise pipe. I'm suspecting this because you say it's only on acceleration. It could be an HVAC issue but you'd think that would happen all the time, regardless of acceleration.
 

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2007 3.2 VR6 Quattro Roadster
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@ TT'sRevenge - Good point. I was also wondering it it might be the clip on the turbo....since sound travels...it might be engine related and not actually in the dash...?
 

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@ TT'sRevenge - Good point. I was also wondering it it might be the clip on the turbo....since sound travels...it might be engine related and not actually in the dash...?
Wastegate arm rattle is a possibility but S cars have a K04 from factory and most (if not all) of them have an adjustable wastegate arm which is much less susceptible to this problem. If it is wastegate rattle the arm can be tightened up with the threaded adjustment--no clip required ;) Also this would fix play in the wastegate itself, not just play on the arm.
 
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If that's the electronic (speaker/transducer) soundaktor then would not be that; instead it has the intake-piping soundaktor (but not every car has this). On the S, it's easily seen on the DV elbow up front of the engine. The version with the noise pipe has an additional path which is where the noise pipe connects--the right hand side when facing into the engine bay. The cars without the noise pipe only have one side coming in from the left, which leads to the turbo.

It was covered in this thread here on the forum from some years ago--the first picture in that thread, the noise pipe is circled in red:
 
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