Originally Posted by Trojan Horse
Maybe you have a bearing going bad in the alternator, water pump, power steering pump, smog pump or it could be the AC compressor clutch?
Originally Posted by Jeff44
Wonderful, lol. How can I test to rule out each one
1. Alternator, Water Pump, PS Pump, Smog Pump - Use the screwdriver or stethoscope (CAREFULLY) as suggested by dream. Another way is to remove the belt and turn the pulley by hand and "feel" for roughness or hard turning.
2. AC Compressor Clutch - Have someone activate the AC on & off a few time while you stand and watch and listen to the clutch engage and disengage.
Note: Being able to use a listening device such as the screwdriver or stethoscope takes some practice. Listening to a well running engine first at various points will enable you to better determine if something is wrong when using the tool to diagnose an issue. I make it a point to try and go over my engine on occasion during oil changes or other maintenance procedures with my stethoscope just to familiarize myself with its "normal" sounds, so if I do need to use it to diagnose an issue I am better able to identify any strange noises.