Whirring noise on long highway trips

07 Chrysler Town & Country with 86K. It’s been happening off and on for about a year now. On long highway trips when I’m driving fast (maybe more when it’s cold), a whirring noise will build up. It starts quiet and can get really loud. When I get off the highway, the engine noise goes down and the whirring noise is really obvious. I take my foot off the accelerator and the whirring noise continues for about 10 seconds. When I hit the gas again (this time at city speeds, 30 mph or so), the whirring noise instantly comes back and can get high pitched and LOUD, almost like an old police siren.

Last time it happened, I popped the hood to track down the source. It seemed to be coming from the engine block. When you’re looking down at it, it’s coming from the left side, directly under the drive belt (but not the belt).

I’m taking it in to the dealer next week. Any ideas til then?

How is the power steering fluid level? If it’s not low the next time you take it for a long drive have a look at the fluid to see if it has gotten all foamy.