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Discussion Starter #1
I am hoping a reply will say "We see that every week, its..." but would be surprised.


I have a buzz from the rear of the car. Sounds like a resonating license plate, but is is definitely not. ONLY happens over 65 MPH. Does not matter in the least the road surface. Bumps will not trigger it. Speed. Maybe wind?


Feels like it could be inside the hatch but only a guess as I can not pinpoint while driving. Could be underneath. Could it be a catalytic converter internal fin issue? An exhaust hangar?


How is something like this even sleuthed at a dealer? (I am under warranty) Do I take a service writer or mechanic for a ride to be sure they hear what I do?


I have removed everything I can think of that could be the source. Even checked the wheel well pockets. At a loss.


Thanks!


~Bob
 

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If you put the transmission in manual mode, you should be able to narrow down whether it is related to engine speed or road speed by changing gears and running the engine at different RPMs. That should help rule out things like exhaust.

If it is really road speed, that makes me think more of the wheels or drive-line. If it depends on the road surface, it could be tire tread wear or something embedded in a tire like gravel or a small nail. If it is independent of road surface or seems more obvious on a quieter road, then it could be more mechanical in the car itself, whether wheel bearings, brakes, etc.

It could also be something aerodynamic like a piece of body trim or the rear wiper flapping in the wind? That would depend a bit on road speed but would obviously change a lot if you had head/tail/cross winds.

You might also go a step further on the interior... try stowing or completely removing the sliding rear cargo cover and also remove or flip over the rear cargo floor to see if it makes a difference?
 

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Discussion Starter #3
Thanks for the reply. Good idea on manual, but I think I run through RPM's enough to say it is not engine speed related. But shall try this morning. I do know bumps do nothing to cause this.

Yesterday I took out the floor cover, jack, wrenches, etc. Still there. I taped up the rear seat belts. Still there. Removed the sliding cover when this first started. Not much left inside. Not the subwoofer nor spare tire. Both tight and rattle free.

I do not think tires. Only over 65MPH and sound too loud. Something solid hitting something solid. Wiper possible. I have not taped that up, but it appears to be tight enough to not do that. But that would be speed (or wind) related. Shall check.

Dealer says they will send shop foreman out for a ride with me. Will likely try that today. Hope it happens when the doctor is there :)

~Bob
 

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Hmm, sorry I am not sure what else to suggest if you've already gone to those lengths with the interior. I hope you have luck with the shop foreman! I have a few other random ideas but these seem kind of far-fetched to me if it really sounds as prominent as you describe.

First, a fuel pump or vapor recovery system can sometimes produce a lot of noise near the fuel tank, but I've usually heard that descibed as more of a whine or gurgle and not a buzz or mechanical vibration.

Second, the big wagon-like cargo area might resonate and amplify a sound that doesn't actually originate in the rear. So some other piece of trim on the side or bottom of the car might also be the ultimate source of a wind-related noise, if not even something from the front wheels or front axle? Have you looked underneath for loose covers or even some kind of road debris caught on the car? Have you tried cycling all windows and the sunroof to make sure there isn't some sort of small gap or loose weather stripping that resonates with the wind?

I also am not sure if you have quattro, so not sure if you have rear driveline components to think about...
 

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Discussion Starter #5
Foreman was out yesterday :( Got an appt for this morning.

Was hoping wiper could be it, but taped it up and no change.And maybe "buzz" was a wrong description. Closest I can think to describe is how I would expect a loose license plate or frame to sound. But I would also expect that to sound over bumps ant this is only at speeds above 65. It is about the same volume as one would expect from that as well, over the road noise, over the radio at "normal" volume. Baffled.

No way for me to get under the car but hope the dealer will put it up to look. Of course will report what we find.

And yes, Quattro. And all windows was one of the first things I tried after taking out anything in the rear.
 

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Discussion Starter #6
Fixed :)

Loose torx screws holding the outer bumper cover. All makes sense now. Dealer took a long ride, baffled, then got under.

Maybe this will help someone else regain their sanity:)

Thanks for all the suggestions.

~Bob
 
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