Range Rover Classic. Manual — part 54
26
COOLING SYSTEM
RANGE ROVER
4
DESCRIPTION AND OPERATION
Operation
The viscous unit consists of two principal components:
An inner member 1 which is secured to water pump
spindle and is driven by the fan belt.
An outer member 2 which has the fan blades
attached, houses the working parts and is driven
through the medium of the viscous fluid.
The inner and outer members have interlocking
annular grooves machined in each, with a small
running clearance 3 to allow the silicone fluid to
circulate through the valve plate 4.
The unit also contains a valve 5 which is controlled by
an external bi-metal thermostat 6.
Starting engine from cold
During the time the engine is at rest the silicone fluid
drains down, half filling chambers A and B. Thus when
the engine is first started sufficient fluid is present in
chamber A to provide a positive drive between the
members, as is evident by the initial noise of the fan.
However within a very short period of time, after
starting the engine, the fan speed and noise will
decline indicating that the fluid is being centrifuged
into chamber B (as seen in RR3757M) causing the
drive to slip.
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.
V8i
5
DESCRIPTION AND OPERATION
Hot conditions
When operating in high ambient temperatures or
when stationary in traffic, the bi-metal 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)
V8i
1
FAULT DIAGNOSIS
ENGINE OVERHEATING
Before conducting any cooling system diagnosis:
See
Description and operation, Engine Cooling
1. Is coolant level correct?
NO -
Allow engine to cool, top up level to
expansion tank seam.
YES - Continue.
2. Is drive belt tension correct?
NO -
See ENGINE, Repair, Drive Belt -
Check Tension
YES - Continue.
3. Is ignition timing correct?
NO -
See ELECTRICAL, Adjustment,
Ignition Timing
YES - Continue.
4. Is coolant in radiator frozen?
YES - Slowly thaw and drain system.
See
Adjustment, Coolant Requirements
NO -
Continue.
5. Is air flow through radiator restricted or blocked?
YES - Apply air pressure from engine side of
radiator to clear obstruction.
NO -
Continue.
6. Are there any external leaks, from water pump,
engine gaskets or the heater unit?
YES - Investigate and rectify.
See Adjustment,
Coolant Requirements
NO -
Continue.
7. Are fan blades fitted correct way round, concave
side towards engine?
NO -
Rectify.
YES - Continue.
8. Is viscous unit operating correctly?
See
Description and operation, Viscous Fan
NO -
Renew.
See Repair, Viscous
Coupling, Fan Blades, Pulley and Fan
Cowl
YES - Carry out a pressure test on radiator cap
and system. Check thermostat type,
operation and correct fitting
See Repair,
Thermostat
If pressure test leads you to suspect coolant
leakage across gaskets, go to check 11,
otherwise: Continue.
9. Are the air conditioning fans operating correctly?
See Electrical Trouble Shooting Manual.K5
NO -
Rectify.
YES - Continue.
10. Is temperature sender and gauge giving
accurate readings?
NO -
Substitute parts and compare readings.
YES - Continue.
11. Carry out cylinder pressure test to determine if
pressure is leaking into cooling system causing
over pressurising and loss of coolant.
If problem is not diagnosed, check the coolant system
for engine oil contamination and engine lubrication
system for coolant contamination.
If the coolant only, or both systems are contaminated,
suspect cylinder head gaskets or radiator.
If only the lubrication stystem is contaminated with
coolant, suspect inlet manifold or front cover gaskets.
26
COOLING SYSTEM
RANGE ROVER
2
FAULT DIAGNOSIS
ENGINE RUNS COLD
Before conducting any cooling system diagnosis:
See
Description and operation, Engine cooling
1. Check operation of viscous unit.
See
Description and operation, Viscous Fan
Is viscous unit operating correctly?
NO -
See Repair, Viscous coupling, fan
blades, pulley and fan cowl
YES - Continue.
2. Is thermostat correct type and operating?
See
Repair, Thermostat
If problem is not diagnosed: Continue.
3. Are the air conditioning fans operating
continuously?
YES -
See Electrical Troubleshooting Manual
NO -
Continue.
4. Is temperature sender and gauge giving
accurate readings? Substitute parts and
compare readings. If problem is not diagnosed
repeat tests, starting at 1.
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