1995 LAND ROVER DISCOVERY engine

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DESCRIPTION AND OPERATION Plenum chamber heating
Air entering the plenum chamber is heated by a flow
of coolant from the inlet manifold which returns
through a long hose, to the top right corner of the
radiator.
1. Hot water supply
2. Cold return to radiatorVISCOUS FAN
Description
The viscous drive unit for the engine cooling fan,
provides a means of controlling the speed of the fan
relative to the running temperature of the engine. The
viscous unit is a type of fluid coupling, which drives
the fan blades through the medium of a special
'silicone fluid' injected into the unit during
manufacture.
1. Drive in from water pump spindle
2. Drive out to fan blades
3. Bi-metal

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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.

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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.

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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 Trouble Shooting
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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ADJUSTMENT COOLANT REQUIREMENTS
Frost precautions and engine protection.
Cooling systemMUST ALWAYSbe filled and
topped-up with solution of water and anti-freeze,
winter and summer.NEVERuse water alone, this
may corrode aluminium alloy.
CAUTION: Do not use salt water otherwise
corrosion will occur. In certain territories
where only available natural water supply
has some salt content use only rain or distilled
water.
Recommended solutions
Anti-freeze:Universal anti-freeze or permanent type
ethylene base, without methanol, containing a suitable
inhibitor for aluminium engines and engine parts.
Use one part of anti-freeze to one part of water.
Anti-freeze can remain in the cooling system and will
provide adequate protection for two years provided
that specific gravity of coolant is checked before onset
of second winter and topped-up with new anti-freeze
as required.
Vehicles leaving factory have cooling system filled
with 50% solution of anti-freeze and water. This gives
protection against frost down to minus 36°C (minus
33°F). Vehicles so filled are identified by a label
affixed to radiator.
NOTE: Should ambient temperatures be
below that stated above refer to
Anti-Freeze Data in Recommended
Lubricants, Fluids and Capacities in Section 09.
Instructions in chart must be strictly adhered to
before driving vehicle.
After the second winter the system should be drained
and thoroughly flushed. Before adding new anti-freeze
examine all joints and replace defective hoses to
make sure that the system is leakproof.
See the 'Recommended Lubricants Fluids and
Capacities' for protection quantities.
See
LUBRICANTS, FLUIDS AND CAPACITIES,
Information, Recommended Lubricants and
Fluids
COOLANT
Service repair no - 26.10.01
Draining
WARNING: Do not remove expansion tank
filler cap when engine is hot. The cooling
system is pressurised and personal
scalding could result.
See coolant requirements before refilling system.
1.Remove expansion tank filler cap by slowly
turning it anti-clockwise, pause to allow pressure
to escape. Continue turning it in same direction
and remove.
2.Remove radiator filler plug and 'O' ring to assist
drainage.

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ADJUSTMENT 3.Disconnect bottom hose from radiator. Drain
coolant into a clean container. Reconnect bottom
hose, re-tighten hose clamp.
NOTE: It is not possible to drain all coolant
retained in heater system. It is not
desirable to flush through system, after
draining.
4.Remove engine drain plugs, one each side of
cylinder block, beneath exhaust manifolds. Drain
coolant, refit and tighten plugs.
5.Pour correct solution of water and anti-freeze
into expansion tank until radiator is full.
6.Start engine, run it until normal operating
temperature is attained, topping up as
necessary.
7.Refit radiator filler plug and 'O' ring, with new 'O'
ring if required. Tighten to
6 Nm.
8.Fit expansion tank filler cap.
9.Allow engine to cool, check coolant level. Finally
top up expansion tank until level reaches seam
of expansion tank.

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REPAIR EXPANSION TANK
Service repair no - 26.15.01
Remove
WARNING: Do not remove expansion tank
filler cap when engine is hot. The cooling
system is pressurised and personal
scalding could result.
1.Remove expansion tank filler cap by first turning
it slowly anti-clockwise, pause to allow pressure
to escape. Continue turning in same direction
and lift off.
2.Disconnect two hoses from bottom of expansion
tank, allowing coolant to drain into a suitable
container.
3.Remove three fixing bolts, remove expansion
tank.
Refit
4.Reverse removal procedure.
5.Replenish cooling system.
6.Check for leaks around all hose connections.VISCOUS COUPLING, FAN BLADES, PULLEY AND
COWL
Service repair no - 26.25.19 - Viscous coupling
and fan assembly
Service repair no - 26.25.03 - Water pump pulley
Service repair no - 26.25.05 - Fan blades
Special tools:
LRT-12-093
LRT-12-094 - Viscous coupling removal
Remove
1.Disconnect battery negative lead.
NOTE: 4.0 V8 only:
Release coolant hose from cooling fan upper
cowl.
2.Release 2 clips securing cooling fan upper cowl.
Remove cowl.

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REPAIR RADIATOR
Service repair no - 26.40.01
Remove
1.Drain cooling system.
See Adjustment,
Coolant
2.Remove viscous coupling and fan assembly.
See Viscous Coupling, Fan Blades, Pulley
and Fan Cowl
3.Release 2 clips and remove fan cowl.
4.Disconnect radiator top hoses.
5.Disconnect four transmission and engine oil
cooler connections to radiator end tanks. Note oil
spillage will occur when connections are
loosened. Blank off exposed oil connections.
6.Disconnect transmission oil temperature sensor.
7.Remove radiator securing brackets from each
side.
8.Remove radiator unit by lifting from its location.
Check condition of rubber mounting pads.Refit
9.Reverse removal procedure.
10.Clean unions and apply sealant.
11.Lubricate new 'O' rings before fitting.
12.Check radiator sealing strips are securely
located.
13.Transfer oil cooler adaptors if fitting new radiator.
14.Ensure that oil cooler connections are tightened
to
30 Nm.before fitting fan blades and cowl.
15.Clean coolant/oil spillage from vehicle.
16.Check all connections for coolant/oil leaks.