Cold Engine Screech... Turbo?

[J77TDC]

Hi All,

I have a 2009 E70 35D which has just hit 90k miles and recently it has started to screech when the engine is cold. It seems to happen when the turbo kicks in as if I keep the revs low enough with minimal load on the engine, the noise doesn't happen. Once the engine starts to warm up (depending on the ambient temp but usually only a few miles) the noise abates no matter what revs or load the engine is under. It is almost like when you hear squealing fan belts on older cars in winter but I'm not so sure it is quite that simple.

I have also started to notice that the turbo 'woosh' seems louder, especially when lifting off the throttle. This could just be a coincidence and possibly just that I never noticed it before though I guess...

I plan on taking it in for some investigation but would appreciate any advice or ideas from anyone who may have experienced similar.

Apologies for the very non technical nature of my post, I'm comfortable with basic mechanics but anything too in depth is a bit beyond me I'm afraid.

Big thanks in advance for any help or advice.
Jim

[X5Sport]

Are you sure it isn't the water pump, or one of the belts slipping rather than one of the two turbos?

[J77TDC]

Nope, not sure at all but great shout, thank you

I'll see if I can figure out where abouts the noise is coming from for a better idea.

Thanks again for the reply.
Jim

[Horizon]

My money's on one of the auxiliary drive bells too, see if the noise changes if you put the air con on whilst it's making the noise to see if it gets worse, as that will put more load on that belt.
Years ago before poly flat belts it was a common problem. I'm sure all on here over 45 will remember

[Craney]

Any update on this as ours does that too.  It seems to me as it makes the noise as one of the turbo comes in.