OK, you kind of hear this noise at low speed and really hear it above 2500 RPM? Try this, with the engine off spin the fan by hand, does it turn with some resistance and spin for one rev or so or is it real stiff and hard to turn? Next start the engine, listen to the fan, while listening closely bring the engine speed up to 2500-3000 RPM, did the fan get quiet? It should have, if your's isn't, it sounds like a visco fan clutch gone south.
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72
'02 CLK320 Cabriolet - wifey's mid-life crisis
2012 VW Jetta Sportwagon TDI...at least its a diesel
Non illegitemae carborundum.