I heard squeaking noises from the engine and decided to replace the idler pulley bearing. This was determined by listening closely to different areas around the engine while it was making noise. You switch the AC on and off, and also turn the sterring wheel back and forth to work the PS pump. Then I narrowed it down by removing the PS / AC belt and running it again.

The idler pulley bearing is pressed in the steel pulley, so you will need a small press or arbor to replace the bearing. When installing the new bearing, you must press on the outside race of the bearing (use a large socket, short steel pipe, etc.) Do NOT press on the inner race or middle seal/cover to install a bearing. The bearing has to be pressed all the way into the pulley so the pulley will line back up with the PS belt.
This bearing is a common type 6303 bearing, double sealed. The size is 17mmID x 47mmOD x 14mm. I found a few replacement parts below. Google "6303 bearing" will lead you to many more sources.
Original bearing part number - NSK 6303DU2
MSC Industrial Supply - #35434802 (Import) $11, #45668118 (SKF) $22
Grainger - #6L052 $18

 

Good info, thanks for this. Mine isn't making any noise but I noticed a few months ago that it's beginning to sweat a little....so I'm not sure how long I have.