Hollow whistling noise...

[s70glt novice[Will]]

98 s70 glt- maintenance/upgrades in sig

So, when i accelerate to above 2500 rpm, then let of the gas suddenly, a hollow noise comes from the left of the engine bay, it sounds like escaping air, and the modulation of the tones sounds like something spinning.

Here are some videos, I have gotten the check engine light taken car of since then (PO172, the vacuum elbow on the left of the intake mani)



pretty weird, and I'm installing a 16t+ ARD Green tune soon, so would like to get that figured out.
Once again:
No CEL
New exhaust (no change of sound)
Clean PTC
Have NOT done PCV
New vacuum hoses
Vacuum at idle is ~20 hg
Boosts up to 6-7 PSI

Thanks for the help!

*EDIT* Not my heavy breathing....i think i was right near the mic... lol.

[vjaneczko]

Blow off valve or engine mount maybe?

[jblackburn]

It's something on the turbo. I can't tell if it's the CBV making that noise (it's a different sound on the big turbos, and happens at high RPM, but the 13 is at full boost by 2500-3000 RPM) or a turbo bearing.

Sounds like this to me:
https://www.matthewsvolvosite.com/forums ... 18#p137818

[s70glt novice[Will]]

i have a boost gauge, and have installed the ipd HD CBV, because of the noise...old cbv was fine, and the problem persisted. however, i do not have full boost by 2500 rpm....not even close. its at 0 pressure then. (no hg/psi) my upper engine mount is in good shape, what other mounts are on that side of the car? it also doesnt happen when dropping from higher engine rpms, above 3k.

Might be a bearing, like jblackburn suggested, if it is, i dont care as im getting the new 16t and tune soon, until then, more suggestions are very helpful. and when i do install it, ill check the old 13g for play and wear etc... and let you guys know if the problem keeps coming. Thank you!

[phat78ta]

That is turbo let off. My 850 does the same thing. I have a steeper driveway but short, and mine does that going up it. However, you should be getting boost (5 or more psi) before 2500 rpms.Check all your intercooler hoses and the bottom of the intercoller itself. I got a hole in the bottom of my cooler and it wouldnt boost at all. but it was a quarter sized hole. Damn parking curbs....

[asimba2]

Sounds like a coked turbo bearing to me. My car is bone-stock and when I'm in the garage with walls all around me, raising the RPMs from idle to even just 1200 RPMs I can hear the turbo spin up and down. Try it and see if you get the sound everytime it spins down. If it's a bypass/blow off valve issue it will only do it under boost--and certainly you won't be making any boost in the garage.

[jblackburn]

I love hearing the turbo spin down when you shut the car off. Such a cool noise

[rspi]

I would think it was the turbo un-winding. I never hear mine wind down when I turn the car off.

I did go test drive a 850 Turbo once that had a BOV and some other thing hooked up on it do amplify the turbo sounds. It also had a small hole in the fire wall which allowed more of the turbo noise to enter the cabin. It was the funest test drive I ever went on. I/we could hear ever sound the turbo made. I thought something was alive near my feet at first. LOL

[s70glt novice[Will]]

My car does it even with 0 psi, and in the vacuum too. i can take another video, but with the new 16t on its way, we'll be able to determine the cause. Also, about the hole in the intercooler line and intercooler, theres a pin-sized hole on the bottom right of the radiator/ inter cooler (i dont know which is which ) i may try covering it with duct tape or something, but am slightly fearful that my "waste gate adjustment" could do some damage. I did two full turns tighter, thinking that was the problem of my little boost. turns out i still dont have enough to meet stock .

[s70glt novice[Will]]

The noise went away with the new turbo!