2002 LAND ROVER DISCOVERY cooling

COOLING SYSTEM - TD5
26-1-10 DESCRIPTION AND OPERATION
Operation
Coolant flow - Engine warm up
Refer to illustration.

+ COOLING SYSTEM - Td5, DESCRIPTION AND OPERATION, Cooling system coolant flow.
During warm up the coolant pump moves fluid through the cylinder block and it emerges from the outlet housing. From
the outlet housing, the warm coolant flow is prevented from flowing through the upper and lower radiators because
both thermostats are closed. The coolant is directed into the heater circuit.
Some coolant from the by-pass pipe can pass through small sensing holes in the flow valve. The warm coolant enters
a tube in the thermostat housing and surrounds 90% of the thermostat sensitive area. Cold coolant returning from the
radiator bottom hose conducts through 10% of the thermostat sensitive area. In cold ambient temperatures the engine
temperature can be raised by up to 10
°C (50°F) to compensate for the heat loss of the 10% exposure to the cold
coolant return from the radiator bottom hose.
At engine speeds below 1500 rev/min, the by-pass valve is closed only allowing the small flow through the sensing
holes. As the engine speed increases above 1500 rev/min, the greater flow and pressure from pump overcomes the
light spring and opens the by-pass flow valve. The flow valve opens to meet the engine's cooling needs at higher
engine speeds and prevents excess pressure in the cooling system. With both thermostats closed, maximum flow is
directed through the heater circuit.
The heater matrix acts as a heat exchanger reducing the coolant temperature as it passes through the matrix. Coolant
emerges from the heater matrix and flows to the fuel cooler 'T' connection via the heater return hose. From the fuel
cooler the coolant is directed into the coolant pump feed pipe and recirculated around the heater circuit. In this
condition the cooling system is operating at maximum heater performance.
Coolant flow - Engine hot
As the coolant temperature increases the main thermostat opens. This allows some coolant from the outlet housing
to flow through the top hose and into the radiator to be cooled. The hot coolant flows from the left tank in the radiator,
along the tubes to the right tank. The air flowing through the fins between the tubes cools the coolant as it passes
through the radiator.
A controlled flow of the lower temperature coolant is drawn by the pump and blended with hot coolant from the by-
pass and the heater return pipes in the pump feed pipe. The pump then passes this coolant, via the cylinder block, to
the oil cooler housing, cooling the engine oil before entering the block to cool the cylinders.
When the fuel temperature increases, the heat from the fuel conducts through the fuel cooler 'T' connection and
causes the fuel thermostat to open.
Pre EU3 models: Coolant from the cylinder block flows through the oil cooler and via a pipe and hose enters the
lower radiator. The coolant in the lower radiator is subjected to an additional two passes through the lower radiator to
further reduce the coolant temperature. From the lower radiator the coolant flows , via a hose, to the fuel cooler.
As the hot fuel cools, travelling slowly forwards through the cooler, it meets the progressively colder coolant travelling
in the opposite direction from the lower radiator.
EU3 models: Coolant from the cylinder block flows through the oil cooler to the EGR cooler and then back to the
expansion tank. and via a pipe and hose enters the lower radiator. The lower temperature coolant from the oil cooler
housing is subjected to an additional two passes through the lower radiator to further reduce the coolant temperature.
From the lower radiator the coolant flows , via a hose, to the fuel cooler.
As the hot fuel cools, travelling slowly forwards through the cooler, it meets the progressively colder coolant travelling
in the opposite direction from the lower radiator.

COOLING SYSTEM - TD5
DESCRIPTION AND OPERATION 26-1-11
Viscous fan operation
A= Cold, B= Hot
1Drive plate
2Fan body
3Clearance
4Valve plate
5Valve
6Bi-metallic coil7Fluid seals
8Ball race
9Fluid chamber
10Reservoir
11Return port
When the engine is off and the fan is not rotating, the silicone fluid stabilises within the fluid chamber and the reservoir.
The fluid levels equalise due to the return port in the valve plate being open between the fluid chamber and the
reservoir. In this condition, when the engine is started, silicone fluid is present in the fluid chamber and causes drag
to occur between the drive plate and the body. This causes the fan to operate initially when the engine is started.
As the fan speed increases, centrifugal force and a scoop formed on the fluid chamber side of the valve plate, pushes
the silicone fluid through the return port in the valve plate into the reservoir. As the fluid chamber empties, the drag
between the drive plate and the body is reduced, causing the drive plate to slip. This reduces the rotational speed of
the fan and allows it to 'freewheel'.
When the coolant temperature is low, the heat emitted from the radiator does not affect the bi-metallic coil. The valve
remains closed, preventing fluid escaping from the reservoir into the fluid chamber. In this condition the fan will
'freewheel' at a slow speed.

COOLING SYSTEM - TD5
26-1-12 DESCRIPTION AND OPERATION
As the coolant temperature increases, the heat emitted from the radiator causes the bi-metallic coil to tighten. This
movement of the coil moves the valve to which it is attached. The rotation of the valve exposes ports in the valve plate
which allow the silicone fluid to spill into the fluid chamber. As the fluid flows into the clearance between the annular
grooves in the drive plate and body, drag is created between the two components. The drag is due to the viscosity
and shear qualities of the silicone fluid and causes the drive plate to rotate the body and fan blades.
As the coolant temperature decreases, the bi-metallic coil expands, rotating the valve and closing off the ports in the
valve plate. When the valve is closed, centrifugal force pushes the silicone fluid through the return port, emptying the
fluid chamber. As the fluid chamber empties, the drag between the drive plate and the body is reduced and the body
slips on the drive plate, slowing the rotational speed of the fan.

COOLING SYSTEM - TD5
ADJUSTMENTS 26-1-13
ADJUST ME NTS
Drain and refill
$% 26.10.01
WARNING: Since injury such as scalding could
be caused by escaping steam or coolant, do not
remove the filler cap from the coolant expansion
tank while the system is hot.
Drain
1.Visually check engine and cooling system for
signs of coolant leaks.
2.Examine hoses for signs of cracking, distortion
and security of connections.
3.Position drain tray to collect coolant.
4.Remove expansion tank filler cap.
5.Remove drain plug access cover from
underbelly panel.
6.Remove drain plug from coolant pump feed
pipe and allow cooling system to drain. Discard
drain plug sealing washer.
Refill
1.Flush system with water under low pressure.
Do not use water under high pressure as it
could damage the radiator.
2.Fit new sealing washer to drain plug. Fit and
tighten drain plug in coolant pump feed pipe.
3.Fit access cover to underbelly panel.
4.Prepare coolant to required concentration.

+ CAPACITIES, FLUIDS AND
LUBRICANTS, Anti-Freeze Concentration.5.Remove bleed screw from top hose.
6.Unclip the bleed hose from the battery box.
7.Unclip the expansion tank from its mounting
bracket, remove the expansion tank cap and
raise the expansion tank vertically 10 cm (4 in).
Retain the tank in this position.
8.Slowly fill the system through the coolant
expansion tank until a steady flow of coolant is
emitted from the bleed hole.
9.Fit the bleed screw, then, with the expansion
tank still raised, continue filling the system until
coolant level reaches the cold level mark on
expansion tank.
10.Fit expansion tank filler cap, fit the expansion
tank to its mounting bracket and clip the bleed
hose to the battery box.
11.Start and run engine until normal operating
temperature is reached, and check for leaks.
12.Switch off engine and allow to cool.
13.Check for leaks and top-up coolant to the cold
level mark on expansion tank

COOLING SYSTEM - TD5
26-1-14 ADJUSTMENTS

COOLING SYSTEM - TD5
REPAIRS 26-1-15
REPAIRS
Fan - viscous
$% 26.25.19
Remove
1.Release fixings and remove battery cover.
2.Disconnect battery earth lead.
3.Remove 3 bolts and remove engine acoustic
cover.
4.Remove upper fan cowl.
5.Remove viscous fan using tool LRT-12-093
and tool LRT-12-094.
RH thread.
Refit
1.Position viscous fan and tighten using tool
LRT-12-093 and tool LRT-12-094.
2.Fit upper fan cowl.
3. Fit engine acoustic cover and tighten bolts.
4.Connect battery earth lead.
5.Fit battery cover and secure with fixings.
Radiator
$% 26.40.01
Remove
1.Drain cooling system.

+ COOLING SYSTEM - Td5,
ADJUSTMENTS, Drain and refill.
2.Remove intercooler.

+ ENGINE MANAGEMENT SYSTEM -
Td5, REPAIRS, Intercooler.
3.Remove clip and disconnect bleed hose from
radiator.
4.Release clip and disconnect top hose from
radiator.
5.Release clip and disconnect bottom hose from
radiator.
6.Release clip and disconnect engine oil cooler
hose from radiator.
7.Release clip and disconnect fuel cooler hose
from radiator.

COOLING SYSTEM - TD5
26-1-16 REPAIRS
8.Remove securing screw and release gearbox
oil cooler from radiator.
9.Remove radiator.
10.Remove rubber mountings from base of
radiator.
11.Remove 2 captive nuts from radiator.
12.Remove sealing strip from radiator.
13.Remove cowl retaining clips from radiator. Refit
1.Fit cowl retaining clips to radiator.
2.Fit sealing strip to radiator.
3.Fit nuts and rubber mountings to new radiator.
4.Fit radiator.
5.Fit gearbox oil cooler to radiator and secure
with screw.
6.Connect fuel and engine oil cooler hoses to
radiator and secure with clips.
7.Connect bottom and top hoses to radiator
secure with clips.
8.Connect bleed hose to radiator and fit clip.
9.Fit intercooler.

+ ENGINE MANAGEMENT SYSTEM -
Td5, REPAIRS, Intercooler.
10.Refill cooling system.

+ COOLING SYSTEM - Td5,
ADJUSTMENTS, Drain and refill.

COOLING SYSTEM - TD5
REPAIRS 26-1-17
Thermostat
$% 26.45.09
Remove
1.Drain cooling system.

+ COOLING SYSTEM - Td5,
ADJUSTMENTS, Drain and refill.
2.Remove viscous fan.

+ COOLING SYSTEM - Td5, REPAIRS,
Fan - viscous.
3.Loosen clips and release air intake hose from
EGR valve.
4.Remove air intake hose.
5.Release 3 clips and disconnect coolant hoses
from thermostat.
6.Remove thermostat. Refit
1.Position thermostat, connect hoses and secure
with clips.
2.Position air intake hose to EGR valve, connect
hose to intercooler and tighten clips.
3.Fit viscous fan.

+ COOLING SYSTEM - Td5, REPAIRS,
Fan - viscous.
4.Refill cooling system.

+ COOLING SYSTEM - Td5,
ADJUSTMENTS, Drain and refill.