Odd turbo noise

[J-Rod]

Sounds like a bird tweeting when the boost is in/past yellow. Like a whistle. I just picked it up from having the flex pipe replaced and now I can hear it.

What could it be? No smoke on startup, no smoke while driving, boosts fine, holds boost, just makes this odd sound.

[Sparky's 9-5 3t]

Is the sound coming from underneath the car when you accelerate?

[J-Rod]

Its hard to tell where its coming from. Sounds more like the front of the car.

[jk88]

My c900 was making an odd high-pitched sound under boost and it turned out to be that I was missing a bolt on the front end of the exhaust manifold. This caused a small gap between the mani and the head, so the air being pushed through was causing the noise. It would go away when the car was warm and the metal expanded, closing the gap.

[Sparky's 9-5 3t]

Originally Posted by J-Rod

Its hard to tell where its coming from. Sounds more like the front of the car.

Pop the hood and have someone rev the motor while you poke around under the hood. If you're not hearing it from there.....

.....roll the windows down and drive through your local downtown area where the buildings are close to the road. Accelerate (safely, of course) when the buildings are close to the sides of the car. You'll be able to hear the sound bouncing back to you from the buildings you're passing and should be able to tell if it's coming from the left or right side. Freeway underpasses don't work, they bounce the sound too much.

I'm speaking from experience. Replaced my flex-pipe a few weeks ago (just the flex portion, welded/clamped in). A week after replacement I developed a whistling noise from underneath the car. Drove through downtown with windows down, revving a few times. Got more whistling from the passenger side than driver. Crawled under the car and took a closer look at the passenger side of the flex pipe. There's a small hole by the clamp where exhaust is escaping. When exhaust air passes over the hole, it creates a whistling sound (ever blow across the top of an empty bottle?). I haven't bothered to fix it because as long as I can tolerate it and it's not obnoxious, I'll deal with it until I finally decide to run full 3" exhaust. Also, the whistling is about as loud as the turbo sound from my CAI, so it doesn't really bother me.

My guess is that the installer didn't properly install a gasket or there's a gap where the new pipe meets up with the existing pipes.

Good luck man

[J-Rod]

Thank you for the very detailed reply Sparky! That sounds exactly like my issue. The sound sounds like air escaping (thus I was thinking a valve or something busted on the turbo)

Yep, sounds just like a CAI. Funny you mention that, because as soon as I got home after first driving it I checked to make the sure the bottom of the filter housing was still there!

I'll try to get out with the car tomorrow and crawl under and check everything out. I can't even hear the sound with the windows up.

[Sparky's 9-5 3t]

Same here, can't hear it with the windows up.

Good luck buddy!

[J-Rod]

Here's what it sounded like:

Saab 9-5 Whistling - YouTube

Saab 9-5 Whistling - YouTube

Turns out it was an exhaust leak. From the manifold, like JK said. My mechanic looked at it today and said I need a new manifold gasket. Taking it back next Friday to have him fix it. It will be nice to have a car that doesn't take make any weird/annoying noises.