This problem has been present for a while now. I've replaced the alt and tensioner pulley but I'm still getting a whirring sound. My A/C doesn't work but it's been out of commission since long before the sound. any suggestions?
Alex
Possible idler pulley.
When I did my 3L swap, the timing cover with both the idler and tensioner pulley were left out in the rain for a while. When I got the car running both pulleys were extremely loud.
Replacing both pulleys, it was perfect.
The bearing in my A/C pulley was shot. Put a new one on a it was perfect. I suspect one of the bearings in your pulley system is gone.
Get a bearing probe. Kind of like a stethoscope with a metal rod (about $15-$20). Check out each piece. I replaced a power steering pump, idler, and tensioner before I got this tool. The only things left were the AC and alt. Got under, and it was quite clear it was an alt. bearing. Replaced the alt., and now sounds like new!
Good luck