Hopefully someone can clarify the correct operation of a clutch fan on a 1991 300CE. A buddy of mine just had the clutch fan replaced on his 1991 300CE and the owner (mechanic) that claims to have 32yrs of MBZ experience at Silver Star Mercedes in Oakland Ca on 17th and Wood Steets says that the 1991 300CE has a Viscous fan that is normally locked up at all times until you reach higher rpms or freeway speeds than it disengages. I was told by another mechanic that the 1991 and the other CE models have a bi metalic type of fan that engages at a preset factory tempature of approx 95 degrees centigrade. He claims that the fan is normally disengaged until the bi metalic spring reaches a preset tempature. Then the clutch fan engages.

Which mechanic is correct?

Thanks for your response.

Phillip