Only 5-cylinder engines
The hydraulic fan creates a continuous airflow through the grille when there is not enough flow from the main electric fan. To extend the life of the auxiliary fan and save energy, Audi has equipped the ribbed V-belt fan with a so-called fluid clutch. At an ambient temperature of approximately 82°C, the hydraulic fan starts to work. This is due to the valve (bimetal plate), through which flows (temperature dependent) oil into the working cavity of the liquid clutch. The oil creates a bond between the V-belt pulley and the fan, which increases the airflow through the grille and reduces the ambient temperature. When the temperature reaches approximately 60°C, the oil flows from the clutch back into the reservoir. After that, the fan rotates by inertia at a lower speed, without expending energy and performing the cooling function.
Problems
The fluid clutch must be replaced if:
When the engine is running steadily, the hydraulic fan is difficult to turn.
The hydraulic fan has a strong axial or radial clearance (a slight gap of up to 15 mm across the fan wheel is acceptable).
Oil is leaking from the fluid clutch chamber.
Unscrew the radiator at the top (left and right) from the front of the engine compartment.
Disconnect the air ducts from the air filter.
To fix, install «carob» key into the holes on the surface of the fan pulley.
Use a 32 wrench to unscrew the fan from the pulley.
Put the fan in the fan tray in the radiator (This «ring» around the fan).
Unscrew the fan drawer.
Carefully pull the side up with the fan.
Unscrew the fan clutch if necessary.
When assembling, tighten the screw with a torque of 70 Nm. If it is tightened too loosely, the fan may become loose and damage the heatsink.
The moment of tightening the fan to the clutch is 10 Nm.
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