2000 Astro A/C Comp. Noise

Noise is coming from the A/C comp pulley. First heard it when I pulled in the garage from work; steady roaring coming from the clutch/pulley area. When I turn the A/C on, and the clutch engages, the noise stops. I left it for a mechanic to look at and he called and said he replaced the belt and had ran it with A/C on and off and never heard anything. I drove it to work again today and did a repeat when I pulled in the garage--same sound; it's a grating kind of sound like maybe bearings? Think maybe the afternoon 30 mile drive is what it takes to get it hot enough to do this? The A/C works fine and now I have a new belt that I don't think I needed. I've been told that the A/C clutch could be replaced. Then someone else told me I'd be better off just doing the entire compressor. Yet another said I could somehow grease the bearings. Any help would be greatly appreciated!

The clutch bearing can be serviced separately. This job requires a special puller to remove the clutch and expose the bearing. Auto Zone rents the puller. Provided the compressor is quiet when the clutch is engaged, no need to replace it. The clutch bearing can not be greased, it is a sealed bearing. You do not have to discharge the A/C system to service the clutch bearing. Here is a link to the bearing:
http://www.partsamerica.com/ProductList.aspx?st=2&parttype=450&ptset=A&searchfor=Clutch+Bearings&so=0

The master is the dude where this stuff is concerned, he's a pro..
but I'll throw one outside the box thought into the mix. If servicing the clutch bearings doesn't get rid of the noise, find a shop that has BG Products. BG has a compressor lubricant that saved me a $1200 compressor replacement about 110K miles ago. (same OEM compressor still going strong).
Mine was making all kinds of noise, it was operating up to spec but was scary sounding. Now, even though I've thrown this out, I'm betting on Old Master's suggestion. The BG lubricant isn't expensive though, cost me $35. You do have to go to a mechanic to get it, BG doesn't sell over the counter as they say.

If it makes noise with the a/c off- and is quiet when on- you probably have a clutch drive that has the air gap a little to tight- causing a metallic scraping or hissing noise- by backing the air gap off a few thousandths- it may solve the problem- but the key here is to determine if the bearing is the cause of the noise- take the belt off and see how well the pulley spins by hand- and if there is any associated noises. If the air gap is rubbing without the compressor turned on- then you can borrow the tool from Autozone to pull out the clutch drive a tad- should be .015-.040" gap between the clutch and the rotating pulley at all times when not engaged. I happen to know a little about these compressors since I do all the warranty return analysis for a living. Good luck

Thanks for all of the valuable input. I noticed the tensioner was jumping a good bit, so I replaced it and haven't heard the noise since.