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Dodge Durango
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Cooling System » Description and operation
Viscous fan drive

DESCRIPTION

CAUTION: Engines equipped with accessory drive belts have reverse rotating fans and viscous fan drives. They are marked with the word REVERSE to designate their usage. Installation of the wrong fan or viscous fan drive can result in engine overheating.

The thermal viscous fan drive is a silicone-fluidfilled coupling used to connect the fan blades to the water pump shaft. The coupling allows the fan to be driven in a normal manner. This is done at low engine speeds while limiting the top speed of the fan to a predetermined maximum level at higher engine speeds.

On all 4.7L an electrical cooling fan located in the fan shroud aids in low speed cooling, It is designed to augment the viscous fan, However, it does not replace the viscous fan.

A thermostatic bimetallic spring coil is located on the front face of the viscous fan drive unit. This spring coil reacts to the temperature of the radiator discharge air. It engages the viscous fan drive for higher fan speed if the air temperature from the radiator rises above a certain point. Until additional engine cooling is necessary, the fan will remain at a reduced rpm regardless of engine speed.

Fig. 17 Fan Blade/Viscous Fan Drive-4.7L/5.2L/5.9L Engines Fig. 17 Fan Blade/Viscous Fan Drive-4.7L/5.2L/5.9L Engines

1 - VISCOUS FAN DRIVE

2 - FAN BLADE

3 - SCREW AND WASHER

Fig. 18 Viscous Fan Drive-4.7L/5.2L/5.9L Engines- Typical Fig. 18 Viscous Fan Drive-4.7L/5.2L/5.9L Engines- Typical

1 - VISCOUS FAN DRIVE

2 - THERMOSTATIC SPRING

3 - MOUNTING NUT TO WATER PUMP HUB

OPERATION

When sufficient heat is present, the viscous fan drive will engage. This is when the air flowing through the radiator core causes a reaction to the bimetallic coil. It then increases fan speed to provide the necessary additional engine cooling.

Once the engine has cooled, the radiator discharge temperature will drop. The bimetallic coil again reacts and the fan speed is reduced to the previous disengaged speed.

    More about «Description and operation»:

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    Thermostat-5.2L/5.9L engines

    Thermostat-4.7L engine

    Radiator pressure cap

    Radiator

    Water pump

    Water pump bypass-4.7L

    Water pump bypass hose-5.2L/5.9L engines

    Automatic transmission oil coolers

    Automatic belt tensioner

    Block heater

    Hose clamps

    Viscous fan drive

    Dodge Durango Service Manual / Cooling System / Description and operation / Viscous fan drive

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