Another "what's that sound" thread
 

Sorry if this has been addressed before. I have done a lot of searching and am at a loss at this point.

Car is stock 2003 6Speed with aftermarket DV's and BMC air filter. 23k Miles.

I am consistently hearing a howling noise that can be best described as air rushing through a pipe (kind of like when you blow air across a bottle opening). I think it is coming from the rear passenger side. This happens in 3rd-6th gear when the RPMs are in the 2700-2800 range and I am cruising with little throttle (no boost registering on the instrument panel).

I brought the car to the shop and the car was diagnosed with a faulty diverter valve, so I had them changed with aftermarket DV's. I also had the power steering reservoir changed as it was squealing. Still the sound continues. It is quite annoying because the howling sound is constant while under cruising RPMs.

Any other ideas of what I should look into? Thanks!

Also, sorry for the newbie TT question, but is it normal to hear a similar winding down sound when exiting the hwy onto off-ramps even when the car is not showing boost?

Are you getting normal, consistent boost? It sounds like you may have an air leak in the turbo piping somewhere on the passenger side.

On your second question, when you say "similar" do you mean the air rushing through a pipe sound? That isn't normal. You shouldn't really hear anything like that.

I don't understand what you mean by saying the power steering reservoir was changed because it was squealing. A reservoir can't squeal, so I assume you mean your steering was making the squealing noise. Normally that's due to low fluid, a bad pump, and/or a loose belt. Changing the reservoir would do nothing to eliminate the sound unless it was leaking and low fluid was causing the sound.

Yes. I am getting normal boost as far as I can tell. For the 2nd question, it sounds like a turbo is spooling down. It can last for 4-5 seconds when slowing down on the off ramp. Again, it sounds like it is coming from the same area.

I had the power steering reservior changed because of this. It was actually squealing. That sound went away after being replaced.
http://youtu.be/ltEw-Jw7c1g

TSB 1/05 4897 Loud Whistling Noise From the Engine Area
"Loud whistling noise from the engine area.

A loud whistling noise can be heard from the engine area while driving the above-mentioned vehicles. The noise can be heard clearly both inside and outside the vehicle. The noise goes away for a short period when pressing the clutch pedal. This noise is caused by the pressure control valve in the steering oil reservoir. This valve vibrates strongly when hydraulic oil flows through it at oil temperatures of more than 212° F. (100° C). To remedy this concern, steering oil reservoirs with a modified pressure control valve have been installed in vehicles manufactured since February 23, 2005."

the conditions under which you heard it, and sound you've described is as close to that ps res "whine" as i can imagine. it sounds much like a "whistling" which is in fact, what it is as the thing vibrates then settles down, usually after engaging the clutch.
my next thought was that maybe you had a wheel bearing going bad, but that IS a decided "growl", as i suggested. but since you've eliminated those two as possibilities... hmm. 4 or 5 seconds?!

can't be a boost leak since it is not under load. your not getting any codes. Did you check the undercarriage for a body panel coming loose? I would lift the car and make sure all is tight underneath. I did have a similar noise once on a non turbo car and it came from the rear diff. Not air related at all. Not saying that is your problem. But sometimes those howling noises can be something totally different. Tires make those noises as well sometimes. When I get strange noises it bugs the hell out of me. Good luck with it.