Hiding Out

Hi.

Just wondering if anyone has had this experience before I talk to the service dept...

During hot & humid weather (90+), I sometimes hear a humming sound (like the wind over a bottle of coke analogy or even worse like wind through a long metal pipe) while moving slowly through traffic in first gear or at a complete stop. Usually, I notice it when idling or up to ~1700 RPMS.

A couple of times I was able to modulate the sound by slowly applying and releasing the brakes (while stopped or coming to a complete stop). Also, I found that I could feel some vibration through the brakes while the humming sound was happening. One time, it lasted almost 10 seconds and grew irritatingly loud while I was playing with the brake pedal (I thought my eardrums were going to burst if it was going to keep going and increase in loudness). I felt the car body actually vibrate and moan with the sound.

One day, a friend decided to turn off the AC when we heard it starting to happen. To my surprise, the sound stopped! He then turned the AC back on, and we heard the sound again except this time it was short and sounded more like it was a popping sound or like pressurized air being released). He turned the AC off again, and we heard the humming/popping sound once more.

Well, I can't seem to reliably duplicate the sound whenever I want. It only seems to happen during hot and humid days. But even then it only seems to happen after idling or driving slowly in traffic for a while (maybe after 20 minutes of driving in traffic or at least driving slowly in hot weather).

Any ideas? TIA!<p>Roberto

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Lake Silver & Ebony 2001 225QC

Lone Starr (Ivan)

when the A/C was turned off, indicates a loose belt to me.

Never heard of that on a TT, though. See your dealer.<p>Ivan
<i>Jacksonville, Florida<i>
<img SRC="http://www.geocities.com/y2ktturbo/tinytt.jpg" BORDER=0>
"Zorro" 2000MY, 180hp, Fronttrak, Silver/Ebony, MKII suspension, spoilTT
K&N, Garmin EMap GPS, Colgan "mask" on order, Cobra R/D

Hiding Out

Thanks for the reply.

I'll remember that when I talk to the service folks. But, I don't think it sounds like a belt. It really sounds like air being released through a pipe or something. My old car had terrible belts and I'm used to hearing taxis with squealing belts while driving through DC. It just doesn't sound the same, but who knows, maybe new loose belts sound different from old loose belts. <p>Roberto

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Lake Silver & Ebony 2001 225QC

Lone Starr (Ivan)

<p>Ivan
<i>Jacksonville, Florida<i>
<img SRC="http://www.geocities.com/y2ktturbo/tinytt.jpg" BORDER=0>
"Zorro" 2000MY, 180hp, Fronttrak, Silver/Ebony, MKII suspension, spoilTT
K&N, Garmin EMap GPS, Colgan "mask" on order, Cobra R/D

Hiding Out

The thing is it doesn't sound like a squeal or a squeek. If you can imagine microphone or amp feedback slowly gaining in loudness and in pitch (starting with the low tones but never getting close to reaching the high-pitched, chalkboard scratching sounds), that would be close to it. In fact, I first thought it was feedback from the stereo, but it's happened without the stereo on.
It just grows loud like alot of air pushing through a pipe or over a bottle.

I thought this sound might be different from the blowoff or diverter valve since it only comes on with the AC, only in the low RPM range (700 to 1700), and only after a bit of driving.

Hopefully, the service people might have heard this happening on other cars, TTs or other Audis (not that that's a good thing)... I'll post a follow-up once I actually get a call back from them. <p>Roberto

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Lake Silver & Ebony 2001 225QC

jamurr

Mine does a similar thing, but it seems when the air conditioner condensor comes on, it makes a loud staccato sound from the front of the car. It seems to be coming from the intake manifold area, although it is difficult to tell. The sound is intermittent; it seems to be worse on hot days. Took it to the dealer and they couldn't reproduce the sound. I'm paranoid because the dealer has replaced the AC condensor stemming from an accident. Is this normal? Any information would be greatly appreciated as I am about to go crazy!!

juliem

Sometimes when I turn the car off, it makes the sound - traveling
thru the pitch like you said...

I may have once heard it on the rpm threshold change between 2000
and 3000rpm, but more often on the engine shutdown.

Not sure if AC was on, though mostly I have it off. I'll try to check
and report back

Hiding Out

Thanks for the replies everyone.

It seems that it might be the diverter valve after all! My service rep said that they have a TT in right now with the same symptoms: low RPMs, AC on, etc. He believes that the diverter valve is going to be the fix. He said that from what he's heard/read, the humming may come on from anywhere near idling to higher rpms.

I'll be scheduling a service appt to get it fixed once the TT that's in right now is fixed.

I can send you an e-mail with his name and phone number in case you need your service rep to compare notes (I hope it's ok with him).<p>Roberto

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Lake Silver & Ebony 2001 225QC