I was out in my 99 Camaro today that I`v owned for a week and it started making a noise. It sounded like one of the pulleys. I went into a store and it carried on after I had re started it but stopped again after a few minutes. After about 20 minutes of driving I came into heavy traffic and it started again. It seems to start when I slow down for a minute or so and clear once I start moving.

 

Could be:
Worn serpentine belt
Bad/noisy idler pulley bearing
Bad idler pulley bearing causing belt mis-alignment
Bad alternator bearings
Worn power steering pump
The A/C clutch is shot
Your best bet would be to remove your belt and give all of your pulleys a twirl by hand. Listen for noise, and feel for wear or slop.

 

Check the idler and tensioner and the bearings in both. I've had one go out on me and shred a belt.

 

Remember the LS1 Camaro's have 2 belts and the 3.8L's have only one.

Massey