help w/bearing noise on 300E passenger side

Help! Got what sounds like a bearing from either the alternator or water pump. Only does it when hot. Doesn't seem to change with engine speed . Is intermittent and seems to start when turning, backing up, or stopping (assume worn bearing is moving up or back on any of those). Lasts from 1-10 seconds. Sound like a bearing. Does seem to be coming from passenger side of engine. Have replaced the heater fan, sagging transmission mount and front flex disk (the latter 2 needed replacing anyhow).

Can't seem to isolate the noise as it stops by the time I get the hood up. Of course I've tried having the wife back up and go forward with me at the open hood but noise won't cooperate.

Assume best way to check is to pull off serpentine belt (ugh) and spin everything. Don't get any play on alternator pulley or viscous fan with belt. Alternator is putting out correct amps and volts at idle and higher RPM's per Autozone check. Water pump replaced 30K miles ago. Car has 151,000 miles.

All suggestions appreciated! Noise is driving wife and me bonkers!