Eerie noise solved (90 300 SEL)!
 

Some time ago I posted a worrisome noise on our 200k mile SEL. After driving for ten or fifteen minutes, a whirring noise devloped that sounded like tranny problems. Several folks posited good ideas, but short of pulling the tranny, I let it go hoping the problem would worsen to the point it could be nailed.

Description: After a cold start, everying was okay until the engine (and therefore tranny) warmed up. Then, a noticeable whine would engage that followed engine revs. All guages normal and car ran fine. It was loud enough to hear over the stereo.

Solution: While doing usual service work (oil, filter checks, etc.), I spun the fan. Hmmmm.....kinda 'soft'. Got engine to normal temp, then checked fan and it still was softer than I expected. Maybe this has to do with the noise?

Got a new fan clutch and the problem is solved! It was the original clutch (well, at least it was an MB clutch) and was working, but when engine heat called for the pin on the clutch to engage, the noise apparently indicated low fluid or damaged internal vanes.

Price of new clutch from Napa was $480
Price of new clutch from MB dealer was $210
Price of new clutch from Fastalane was $156

Hope this helps someone else.

Thanks
 

It's great when members like you contribute correct solutions to weird problems.