LAND ROVER DISCOVERY 1995 Workshop Manual

26COOLING SYSTEM
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 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.

Tdi
1
ADJUSTMENT COOLANT
Service repair no - 26.10.01
Draining
WARNING: Do not remove any caps or
plugs when the engine is hot. The cooling
system is pressurised and personal
scalding could result.
1.Remove expansion tank filler cap.
2.Disconnect bottom hose from radiator and allow
coolant to drain into a container. Ensure
container is clean if reusing coolant.
NOTE: When expansion tank has emptied,
remove thermostat housing plug to assist
drainage. Similarly when coolant level is
below top of radiator, remove radiator plug.
3.Reconnect hose after draining and tighten hose
clamp.
Refit
CAUTION: In order to expel ALL air from
the cooling system, follow the procedures
carefully.
NOTE: Refill procedure is slow but can be
accelerated by squeezing hoses to assist
removal of air from the system.
4.Add correct mix of coolant into expansion tank
until radiator is full (as seen through plug hole on
top of radiator).
See LUBRICANTS, FLUIDS
AND CAPACITIES, Information, Anti-Freeze
CAUTION: Take care to avoid excess
coolant spillage from radiator.
5.Fit radiator plug.
6.Continue adding coolant into expansion tank
until coolant appears in thermostat housing.
CAUTION: Take care to avoid excess
coolant spillage from thermostat housing.
7.Fit thermostat housing plug.
8.Check coolant in expansion tank is level with
indicator post. Add more coolant if necessary.
9.Start engine and run for 5 minutes.
10.Allow engine to cool, check coolant level in
expansion tank; top up to level indicator post if
necessary.
11.Fit expansion tank filler cap.

Tdi
1
REPAIR VISCOUS COUPLING, FAN BLADES, PULLEY AND
FAN COWL
Service repair no - 26.25.03/05
Viscous coupling -Remove1to3
Fan blades -Remove1to4
Fan cowl -Remove1to3
Fan pulley -Remove1to6
Remove
WARNING: Disconnect battery negative
terminal to prevent engine being started
before removing or adjusting drive belt.
1.Slacken nut securing viscous coupling/fan blade
assembly to pulley.
NOTE: Nut securing viscous unit to pulley
has a left hand thread. Release by turning
clockwise when viewed from front of
viscous unit.
2.Drop viscous unit and fan assembly into bottom
of cowling
3.Remove two fixings clips from top of cowling and
lift cowling complete with viscous unit and fan
out of lower mountings.
4.Remove fan blades from viscous coupling if
necessary.
5.Remove serpentine drive belt and, if fitted, air
conditioning compressor belt.
6.Remove pulley fixings, remove pulley.
NOTE: The serpentine belt is removed by
using a hexagonal socket and tommy bar
on the auto-tensioning pulley nut. Whilst
tensioning the device the belt can be removed.
7.Reverse removal procedure. Ensure fan blades
are fitted correctly. Fan is marked 'front' and
should be fitted with word 'front' closest to
radiator. Tighten to
30 Nm.
8.Refit drive belt.See ENGINE, Repair, Drive
Belt
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
begins to open. Thermostat is satisfactory if its
open between 85°C and 89°C.
Refit
7.Insert thermostat with jiggle pin/vent hole upper
most (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.

26COOLING SYSTEM
2
REPAIR WATER PUMP
Service repair no - 26.50.01
Remove
WARNING: Disconnect battery negative
terminal to prevent engine being started
before removing drive belts.
1.Drain engine cooling system.
See Adjustment,
Coolant
2.Remove top hose radiator to thermostat.
3.Remove top hose intercooler to induction
manifold.
4.Slacken water pump and power steering pump
pully retaining bolts.
5.Remove drive belt.
6.Remove centre nut from belt tensioner.
7.Manoeuvre pulley upwards and withdraw
tensioner from retaining stud.
8.Disconnect hose thermostat to bottom hose,
release hose from clip on water pump and move
aside.
9.Remove water pump pulley.
10.Remove power steering pump pulley.
11.Remove 8 bolts securing water pump, noting
location of 3 through bolts.
12.Withdraw pump and gasket, clean all gasket
material from mating surfaces.
Refit
13.Refit water pump in reverse order to removal
using new gasket.RADIATOR
Service repair no - 26.40.01
Remove
1.Drain cooling system.
See Adjustment,
Coolant
2.Disconnect radiator top hose.
3.Remove fan blade assembly.
4.Remove cowl.
5.Disconnect engine oil cooler connections and
turbo intercooler connections from radiator ends.
NOTE: Oil spillage will occur when
connections are loosened. Blank off
exposed oil connections.
6.Disconnect expansion tank bleed hose from
radiator.
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.Check radiator sealing strips are securely
located.
10.Transfer oil cooler adaptors if fitting new radiator.
11.Reverse removal procedure. Tighten oil cooler
connections to
30 Nmbefore fitting fan blades
and cowl.
12.Check all connections for leaks.

V8i
1
DESCRIPTION AND OPERATION ENGINE COOLING
Description
The V8i engine uses a pressurised cooling system
and cross flow radiator which is supplied from a
separate header tank. The coolant radiator also
incorporates a section at the left hand end for cooling
the transmission oil and a section at the other end for
cooling the engine oil.The belt driven viscous fan and centrifugal water
pump is located in the engine front cover with ports for
circulation of coolant to both banks of cylinders and
cylinder heads. Coolant returns to the top of the
radiator via ports in the inlet manifold where the
thermostat is mounted horizontally.
Coolant also circulates through the vehicle heating
system and is used to heat air entering the inlet
manifold plenum chamber.
Coolant circulation (engine hot)
1. Cross flow radiator
2. Header tank
3. Viscous fan and water pump
4. Heater pipes
5. Plenum chamber connection
6. Thermostat

26COOLING SYSTEM
2
DESCRIPTION AND OPERATION COOLANT CIRCULATION
Operation
When the engine is started from cold the thermostat
prevents any coolant circulation through the radiator
by closing off the top hose. During the engine warm
up period, the water pump, pumps coolant around the
cylinders to the rear of the cylinder block along the
main galleries in both cylinder banks. At the rear of
the cylinder block the coolant rises through a large
port in each cylinder head/block joint face, and then
flows forward to connect with ports at the front of the
inlet manifold. From the manifold the coolant is carried
by an external pipe to the heater unit and from the
heater through another external pipe to the pump
inlet.The coolant circulation through the cylinder block and
heads, does not change when normal running
temperature is reached and the thermostat opens. But
with the thermostat open, coolant flows through the
top hose to the radiator where it is cooled and drawn
back into the pump via the bottom hose.

V8i
3
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

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.

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.