Here'* a strange one:

My car started making a bearing noise this morning after I got to work. I pulled the alternator belt and tried spinning the pulleys, but couldn't find anything. So I started the car up, and still had the noise. This meant that one of the accessories on the supercharger / water pump belt was causing the problem.

So i loosened that belt and spun the pulleys, everything was smooth.

But I found a little pebble wedged in-between two of the grooves on the pulley that contacts both belts. It was on the inner one. I don't know how it got in there, but it was the perfect size to stay wedged in there, so that every time the pulley spun one revolution it contacted the belt. I pulled it out with pliers, reassembled the belts and it ran quiet.

Very strange. I feel like I got lucky that I found it.

That'* pretty cool. You could have messed with it for days before you found it. You ever consider the gatorback belts? The design of the tread may have prevented it from happening in the first place. I'm pretty happy with them. Already changed over the SC belt, and I have the new one for the main drive belt sitting on my front seat right now.

Hmmmm...ive been having this same problem, i went ahead and changed the water pump, the power steering pump and also put in a 180 thermo while i was at it. still the same thing, i also had my ALT checked at car quest and was fine, last thing on the list was an A/C compressor @ $340! but yet still i have this annoying sound that embarasses me to even let idle.
Car is now in the shop getting repaired (also had ticks and a slight knock in the motor...but shes getting all doctored up now should run by the garage and see if i too might have a pebble stuck....

If not a pebble, take a good look at the idlers. They usually go first.

It would be hard to imagine how anyone else could have this problem..

But I guess that'* why I posted it. You have to take off the belt to see the pebbles in the pulleys.

Will'* right, don't forget the tensioner pulley.