Cooling Fan
WARNING: This page does not describe the selected car, but rather 16 other vehicles, including the 2004 Mercedes-Benz CLK55, 2004 Mercedes-Benz CLK500, 2004 Mercedes-Benz CLK320, 2004 Mercedes-Benz C320, and 2004 Mercedes-Benz C32. However, it is still accessible from the selected car via links, so may be relevant.
Spin fan wheel by hand several times and check for imbalance or grinding noises, if imbalance or grinding noise is found, replace cooling fan motor with integrated control unit. See COOLING FAN WITH INTEGRATED CONTROL UNIT under REMOVAL & INSTALLATION.