There are two ways to service the clutch fan on the 300E. The right way, and the permanent way.
Right way: Purchase new/rebuilt electromagnetic clutch and install. Refer to a Haynes manual for this operation
Permanent way: When you replace your wiper blades, save the rubber. Cut three pieces appx. one inch in length. Remove the fan from the clutch, and pry the metal ring apart from the fan assembly enough to get the three rubber wedges in between the ring and the fan. Re-install the fan.
The fan will run constantly, but never need maintenance again.
Benzracer