Temperature-controlled viscous fan clutch - RA20001043120X(20-3100)
WARNING: This page does not describe the selected car, but rather 42 other vehicles, including the 1999 Mercedes-Benz S600, 1999 Mercedes-Benz S500, 1999 Mercedes-Benz S420, 1999 Mercedes-Benz S320, and 1999 Mercedes-Benz CL600. However, it is still accessible from the selected car via links, so may be relevant.
Cut-in temperature
At a certain air flow temperature, see switching points of coolant system (20-0020) , acting on the bimetal of the viscous fan clutch, the bimetal alters its shape and causes the fan to cut in, which can be clearly heard.
Safety cut-off
A second (internal) bimetal switches off the fan in a smooth operation in the upper speed range above 4500 rpm, depending on the ambient temperature.
Repairs
A faulty viscous clutch cannot be repaired, and must be replaced.
Transportation and storage
Temperature-controlled viscous fan clutches must be transported upright.
The viscous clutch may be placed down on its flange side for a short period, e.g. for assembly purposes, but it should never be placed down on the front.