OM603...how to diagnose pulley whine?

[sethro]

Hello all,

1987 300tdt with a whine/chirping at idle. Sounds like an idler pulley type whine, but I'm not quite sure how to diagnose and isolate. I'm hoping to not just throw money at this problem and actually only buy the part that needs replacing (what a concept). Serpentine belt is new (last few months). Noise goes away after RPMs rise.

Best bet to buy a mechanic's stethescope and have at it? None of the pulleys *seem* loose/sloppy and there is no unusual serp belt wear.

Where do I start?

thanks in advance,

seth
oakland,ca
1987 300TDT