2005 XC90 Mystery squeal diagnosis help
 

Hello friends - I am hoping someone may be able to help diagnose a mystery squeal sound in the engine.
The vehicle is a 2005 XC90 2.5L w/ 90K miles. The sound only happens on cold start, and starts after a minute or so when the idle drops.
It is fairly loud squealing, and it lasts for a few minutes. Mechanic has said its likely not a belt.
Attaching a video (link below) in case someone can recognize the squeal.
Thanks much for any tips!

http://ge.tt/9yj1nPx2