I'm getting a squeaking scraping noise from one of the ancillary parts on the front of my 1998 (97K miles) C-230 (original owner). The noise seems to change with throttle and A/C operation. Get noise at a steady cruise on the highway and when at idle it seems to be more variable with it's loudness.

I was hoping someone could give me tips on how to determine if it is a water-pump, alternator, smog pump (have one?), or front crankshaft assembly.

Years ago my belt tensioner went bad, what I am getting now does not resemble that and the noise seems to emanate from closer to alternator or water pump.

I tried using a long screwdriver to detect vibration with no luck, I'll try a stethoscope.

Any advice on what a bad water pump bearing sounds like or an alternator bearing failure, would be helpful.