05 S40 T5 Awd- fluttering whistle noise, Turbo?
 

I have a noise that started a few months ago when accelerating. I can best describe it as a fluttering whistle and seems to happen when the turbo engages but not all the time. The car must be warm after driving for around 5-10 minutes before you will notice it. Most noticeable when accelerating from 40 to 50 mph. It isn't the normal turbo spool, much louder and more irritating. Dealership couldn't diagnose it yet.

I have already had the S40 oil trap/pcv warranty repair done and is not the case.

Almost sounds as if a barring in the turbo is going out but I don't notice any loss of power or performance. Maybe some other vacuum leak that doesn't cause a check engine and only starts whistling when the turbo is really spooling hard?

Took it in and the dealership was dumbfounded. They tried saying it was my serpentine tensioners and replaced them but it didn't fix anything.

Does Anyone have any suggestions, any help is appreciated.

If it is the Turbo any advice on a aftermarket replacement (that may add hp) or can these turbo's be repaired.

Thanks

I think i have the same thing in my turbo s40, The dealer heard it to but i kind of like it, Maybe a different sound.