Help with another squealing noise from my D12...

2007 Volvo 780 D12 engine.

This is a weird one. On cold starts I hear a squealing noise coming from the passenger side of the engine. It doesn't start squealing until about 30 seconds after the engine has been running, but then the engine changes tone and then it starts squealing. It only happens at idle speed, if I push down on the accelerator, even just a little bit, the squeal stops. Once the engine is good and warm it stops squealing too. I've never heard it any other time but#at idle speed. It has gotten progressively worse/louder over the last few weeks. Any ideas?

Thanks.

 

That would be great if it was just the belt but it sounds more severe unfortunately. I should mention that if I just press the accelerator slightly and hold it one particular spot while it's squealing, the squeal goes away and I hear air going puff puff puff, like the sound the air governor makes but much quieter, while it's doing that the rpms bounce ever so slightly. This engine has an exhaust pressure governor. I was worried it might be the turbo, but the fact that the squeal goes away and I'm not getting any smoke out of my stack rules that out doesn't it? Does anyone know about those exhaust pressure governors? Could that be it?

 

Now that I really think about it that makes perfect sense. The exhaust pressure governor is there to keep the engine/exhaust temp higher at idle speed, so pressing the accelerator would cause it to disengage and that's when the squeal stops. The air noise I'm hearing could be from that pressure being released too. This making sense? Any Volvo expert or tech have any input?

 

Yeah, the tone change in the engine is caused by the EPG turning on, that's what I thought. Thank you. I know I do have a leak down there too cause I can smell it thru the AC system when idling. Hopefully this is all the same problem.

 

Thank you, but the sound stops when I rev the engine. It's only there when idling, and only when the engine is cold. It stops squealing at about 150 degrees coolant temp from what I observed this morning. Also, I had the manifold gaskets replaced back in November. But I'll check the egrs.