1995 LAND ROVER DISCOVERY lock

26COOLING SYSTEM
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.

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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.

V8i
1
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.

26COOLING SYSTEM
2
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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1
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.

26COOLING SYSTEM
2
REPAIR
3.Use LRT-12-093 to prevent coolant pump pulley
from turning and using LRT-12-094, unscrew
viscous coupling from water pump.
NOTE: Nut securing viscous unit to water
pump has a right hand thread. Release by
turning anti-clockwise when viewed from
front of viscous unit.
4.Remove fan and coupling assembly.
Do not carry out further dismantling if component
is removed for access only.
NOTE: Mark fan with reference to assist
refitting.
5.Remove 4 Allen screws securing blades to
coupling. Remove coupling.
6.Remove serpentine drive belt.
7.Remove pulley fixings, remove pulley.Refit
8.Clean fan blades and mating faces.
9.Fit fan blades to coupling. Secure with screws.
Tighten to
24 Nm.
10.Using LRT-12-093 and LRT-12-094, fit fan
assembly to pump. Tighten to
56 Nm.
11.Fit cooling fan upper cowl. Secure with clips.
12. 4.0 V8 only:Fit coolant hose to cooling fan upper
cowl.
13.Fit serpentine drive belt.
14.Fit pulley fixings, remove pulley.
15.Reconnect battery negative lead.

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3
REPAIR THERMOSTAT
Service repair no - 26.45.01
Remove
1.Partially drain cooling system, until coolant level
is below thermostat housing.
2.Disconnect hose from thermostat housing.
3.Disconnect electrical connections to water
temperature switch.
4.Remove outlet elbow.
5.Withdraw thermostat.
Test
6.Note rating of thermostat is 88°C. Place
thermostat in a container half full of water. Heat
water, observe temperature at which thermostat
opens. Thermostat is satisfactory if it opens
between 85°C and 89°C.Refit
7.Insert thermostat with jiggle pin/vent hole
uppermost (12 o'clock position).
8.Fit the outlet elbow and new joint washer.
Tighten to
28 Nm.
9.Reverse removal procedure. 1 to 3.
10.Check for coolant leaks around all connections
and joint faces.

30MANIFOLD AND EXHAUST SYSTEM
2
REPAIR Remove
Catalysts - remove and refit 1 to 5
1.Raise vehicle on a ramp [hoist].
2. Catalyst vehicles only:Disconnect two heated
oxygen sensor wiring connectors.
NOTE: NAS models have four heated
oxygen sensors fitted.
3.Remove two nuts securing rear exhaust
assembly to front exhaust assembly.
4.Remove nuts and release front downpipes from
manifolds. Discard gaskets.
5.Lower front exhaust assembly with catalysts (if
fitted), retain olive.
NOTE: Assistance is required for removing
and refitting rear exhaust assembly.
6.Remove bolts securing three hanger brackets to
chassis. Lower exhaust assembly onto rear axle.
Detach rubbers from hanging brackets.
7.Place extended axle stands underneath chassis,
in front of chassis mounted rear towing brackets.
8.Lower ramp[hoist] until vehicle weight is
supported securely on stands.
9.Lower ramp [hoist] until rear shock absorbers
are ALMOST fully extended.
10.Move rear exhaust to a diagonal position, centre
silencer to right of vehicle.
11.Facing rear of vehicle, twist assembly
anti-clockwise clear of rear axle.
12.Remove rear exhaust assembly from vehicle.
Refit
13.Position rear exhaust assembly over rear axle in
a diagonal position, as for removing.
14.Twist assembly clockwise until it is in mounting
position.
15.Reverse removal procedure. 1. to 9. using new
manifold gaskets and applying exhaust sealer to
system joint.
16.Examine system for leaks, ensuring that system
does not foul underbody components. Rectify if
necessary.EXHAUST MANIFOLD - V8i
Service repair no - Left hand - 30.15.10
Service repair no - Right hand - 30.15.11
Remove
1.Disconnect front exhaust pipe(s) from
manifold(s).
2.Tap back bolt locking tabs and remove eight
bolts, lock tabs and washers.
3.Remove manifold(s) and old gaskets.
Refit
4.Ensure that mating surfaces of cylinder head
and exhaust manifold are clean and smooth.
5.Coat threads of each bolt with anti-seize
compound.
6.Place manifold and new gaskets in position on
cylinder head and fit securing bolts, new
lockplates and plain washers. Plain washers are
fitted between manifold and lockplates.
7.Evenly tighten manifold bolts to
20Nmbend
over lockplate tabs.
8.Reconnect front exhaust pipe, using new
exhaust flange gaskets.