FAN DRIVE VISCOUS CLUTCH
- 3.9L/4.7L/5.9L
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 overheat-
ing.
The thermal viscous fan drive (Fig. 23) and (Fig.
24) is a silicone-fluid-filled 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 engines 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. 22 Thermostat and Thermostat Housing 4.7L
1 - THERMOSTAT HOUSING
2 - THERMOSTAT LOCATION
3 - THERMOSTAT AND GASKET
4 - TIMING CHAIN COVER
Fig. 23 Fan Blade/Viscous Fan Drive
1 - VISCOUS FAN DRIVE
2 - FAN BLADE
3 - SCREW AND WASHER
7 - 44
ENGINE
AN
ENGINE COOLANT THERMOSTAT - 4.7L (Continued)