Strange sound, like a balloon emptying...

[Samurai Nigel]

I've searched around for an hour or so, but I can't seem to come up with a good answer to this one.

At around 75 mph or so, my '00 S4 begins to make a sound that I can only describe as similar to when you let the air out of a balloon slowly, that high-pitched squealing sound when you pinch it with both index fingers and thumbs and try to annoy the bloke next to you.

It doesn't happen below that speed, it doesn't appear to be boost dependent, as it makes the same sound at full boost or full vacuum. It doesn't appear to be gear or RPM dependent, as I can make the sound happen in both fifth and sixth at that speed, and it doesn't happen in lower gears at lower speeds. The sound is hard to locate, I'd guess it's coming from the engine bay, but it could almost be from somewhere inside the cabin. Putting my ear up to the dash, it's loudest in the direction of the instrument cluster or the center console.

I do have the AWE boost gauge installed, but it doesn't seem like it's coming directly from that, and jostling it around doesn't seem to affect the noise at all. If I accelerate past 75, say, to 100mph, the noise gets proportionately higher pitched as I gain speed, then lower pitched as I lose speed, and then disappears again once I decelerate below around 75 mph or so.

So yeah, I'm completely stumped. Any takers?

Oh, and hooray for first posts.

[Audi S4 Turbo]

I was going to say maybe your fuel pump but that's in the rear. Not sure. Something with your air vent maybe?

[Samurai Nigel]

Hmmm, didn't consider closing down/opening wide the vents. I forgot to mention that I tried replicating the sound with the AC on and off, same sound either way. I'm certain it's not the fuel pump, primarily because that sound would be from the rear, as you say, and if it were fueling-related, I'd think the sound would be closer related to either WOT or high RPM.

I'll try playing with the vents and see if it makes a difference, but feel free to keep the ideas coming!

[Audi S4 Turbo]

Also when the temp air controller goes out it will buzz.

[sCeRaXn]

Thats gonna be a bitch to track down lol. I know you said it was coming from the center console area, but have you tried listening around the shifter? The shifter box could have a small leak in it that only makes that noise at higher speeds. This is a complete and total guess though. Good luck with that one man.

[MiniRS4]

a balloon emptying sounds like flatulation to me. =)

[Caddy7]

sunroof??

[S4-ORCE]

Wind noise? LOL

[01 S4]

Wind noise? LOL

2X

[Overboostin]

a balloon emptying sounds like flatulation to me. =)

+1, maybe you just get nervous driving at that speed and unknowingly let it out. Is the sound accompanied by any smell?

[Samurai Nigel]

Been a long time, but I finally figured out what this was... a pinhole air leak at the top of the windshield above the mirror. Months before, a company had replaced my cracked windshield and apparently there was a tiny leak in the sealant or something. I found it on a day where I was particularly irritated by the sound and so I frantically thrust my ear around the car at 80 mph trying to find the source of the sound. I finally was pretty sure it was up by the mirror, and started pressing around. I realized quickly that I could change the pitch of the whistle by pressing on the glass of the windshield just above and behind the mirror.

Mission accomplished! (Now I just need to fix it...)

[kastro]

im assuming it didn't leak out drops of water cus t'was so tiny? .. but good stuff finding. i hate annoyances

[Samurai Nigel]

Nah, hole seems too small to leak water. Only air, only moving at a reasonable clip, and with variation based on temperature and crosswind speed/direction.

[fdation]

same thing happened to my windshield in my is300 i had ...then it went away after a few weeks

[JoMiDo88]

im assuming it didn't leak out drops of water cus t'was so tiny? .. but good stuff finding. i hate annoyances

yea me too... theyre so annoying right?