I have always heard a slight "spool-up" sound after starting our 2004 s60 2.5T, and I have never really known what it was. While it seems like a turbo spool-up sound, I have had other turbo cars that didn't do this, so I figured it was not the turbo, but some other "pump" of some kind.

As of a day or so ago, the thing spools up and is just plain "roaring" at idle. Has anyone ever experienced this? This car has been well cared for - no extended oil changes or abuse of any kind. It has about 45k miles. I just can't imagine what could be going bad at this point.

A very uneducated guess is that it IS a bearing in the turbocharger but I am no Volvo expert.

 

I have a 2009 S40 2.5T, which I'm guessing is about the same engine...I usually hear two different pitch "spool up" sounds when accelerating. I don't hear anything at idle so I've been assuming that the sounds are related to the turbo.

 

Yeah, this happens basically when you start the engine. It doesn't seem like a turbo because of the way it spools up at idle (as opposed to under acceleration) but I can't imagine what else would sould like that. Basically it sounds like something that starts from zero and goes to a fairly high RPM, and now it is just extra loud, basically "screaming".

I listened to it a little more yesterday and it seems fairly clear that it is at the FRONT of the engine, so that confounds things a bit because that isn't where the turbocharger is located. That might be good news in that whatever it is is probably cheaper than a turbo replacement.