300Tdi Discovery
Tdi
3
DESCRIPTION AND OPERATION
Viscous unit slipping (Engine at normal running
temperature)
1. Inner member (drive in fast)
2. Outer member (drive out slow)
3. Running clearance
4. Valve plate
5. Valve (closed)
6. Bi-metal
7. Fluid seals
8. Ball race
A Fluid chamber
B Fluid chamber
If the engine speed is increased the degree of slip will
also increase to limit the maximum fan speed.
Hot conditions
When operating in high ambient temperatures or
when stationary in traffic, the bi-metel thermostat will
operate and open the valve port between chambers A
and B.
Opening the valve (as shown in RR3758M) allows the
fluid to circulate between the two members, causing
the unit to couple, thus increasing the fan speed and
cooling effect.
Viscous unit coupled (Hot running conditions)
Bi-metal expanded, valve (open)
