Metallic squeak above 1800 rpm - which bearing?

[knick_knack]

M20 in my 1990 325is makes a metallic squealing sound when it is over 1800 rpm. Happens in gear or neutral, clutch in or out. The sound is most pronounced during engine overrun.

I assume the sound is coming from a bearing on a pulley or tensioner, but how do I go about finding which one?

[ahlem]

First thing I would do is remove all your belts and hand spin the components they drive.
Feel any Grinding?
Then I would briefly, i.e. no water pump connected, run the motor for 15 seconds at above 1800 and see if the squeak is absent. Then I would add back accessories one at a time and see when the squeak starts back up.
Did I mention you are going to have a no water pump situation briefly so don't run it hot?
If you hit the suspect bearing with a precision shot of lube and it quiets down, you are there.

[knick_knack]

Thanks ahlem. Would you recommend against trying to hit each bearing with a precision shot of lube and seeing if that fixes the problem before disconnecting all the belts?