Viscous fan (Audi 100 C4)

The main purpose of installing the fan is to save engine power. The fan switches on at a temperature of about 80°C. Switching is done through bimetallic plates, which, depending on the temperature, direct viscous silicone oil through the supply valve into the working space. In this case, the oil forms a strong connection between the pulley and the fan, the fan rotates and blows cold air onto the radiator. If the temperature drops below 60°C, the valves open again and the oil can return from the working space to the waiting space. The fan is not set in motion and rotates slowly, without wasting engine power.

Checking and replacing the viscous fan

If the fan cannot be turned when the engine is not running or there is excessive play (axial and radial), and also if oil leaks are detected on the coupling, then it is necessary to replace the viscous coupling.

To replace it you need:

Screw a 6mm long bolt (2) with an M5 thread into the indicated place to lock the viscous coupling pulley (1) and unscrew the mounting bolt with an 8mm Allen key (3).



Remove the viscous fan.



Disconnect the coupling from the fan.

Connect the new coupling to the fan. The tightening torque is 10 Nm.

Install the viscous fan back. Tighten the bolt to 70 Nm. Do not forget about the unscrewed M5 bolt.