Land Rover Lesson 2 Auto Trans Coolingine Rover Manual

							For additional airflow through the radiator matrix,
particularly when the vehicle is stationary, there is an
engine driven Viscous fan unit fitted to the rear of the
radiator. The fan is used for engine cooling and for Air
Conditioning (A/C) system cooling. The fan is mounted
using a left hand thread.
The viscous fan unit is electronically controlled by the
ECM to optimise fan speed for all operating conditions.
NOTE: If the electrical connections to the viscous fan
are disconnected the fan will idle and overheating may
result. The ECM stores the appropriate fault codes in
this case.
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							ENGINE COOLING SYSTEM OPERATION
Cooling System Coolant Flow, Without Engine Oil Cooler
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							Cooling System Coolant Flow, With Engine Oil Cooler
When the engine is running the coolant pump is driven
by the ancillary drive belt. This forces coolant to
circulate around the engine, heater and EOC, while the
thermostat and bypass valve are shut. As the temperature
and pressure increases the bypass valve is forced open
allowing coolant to circulate through the bypass valve.
When the temperature reaches 82°C (180°F) the main
thermostat begins to open, allowing coolant to circulate
through the main radiator. As the thermostat
progressively opens (fully open at 95°C (203°F)), the
bypass valve progressively closes forcing any coolant
through the heater or radiator. Once coolant is allowed
to circulate through the radiator, the transmission fluid
cooler begins to receive coolant flow.
The increased coolant volume, created by heat
expansion, is directed to the expansion tank through a
bleed hose from the top of the radiator. The expansion
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							tank has an outlet hose which is connected into the
coolant circuit. This outlet hose returns the coolant to
the system when the engine cools.
Coolant flows through the radiator from the top right
hand tank to the bottom left hand tank and is cooled by
air passing through the matrix. The temperature of the
cooling system is monitored by the Engine Control
Module (ECM) via the Engine Coolant temperature
(ECT) sensor located in the cylinder head. The ECM
uses signals from this sensor to adjust fuelling according
to engine temperature.
To control the cooling fan, the ECM sends a Pulse
Width Modulated (PWM) signal to the cooling fan
module (integral to the ECM). The frequency of the
PWM signal is used by the cooling fan module to
determine the output voltage supplied to the fan motor.
The ECM varies the duty cycle of the PWM signal
between 0 and 100% to vary the fan speed. If the PWM
signal is outside the 0 to 100% range, the cooling fan
module interprets the signal as an open or short circuit
and runs the fans at maximum speed to ensure the engine
and gearbox do not overheat.
The speed of the cooling fan is also influenced by
vehicle road speed. The ECM adjusts the speed of the
cooling fans, to compensate for the ram effect of vehicle
speed, using the Controller Area Network (CAN) road
speed signal received from the Anti-lock Braking
System (ABS) module.
Pressure Relief Thermostat (PRT)
The thermostat is exposed to 85% hot coolant from the
engine on one side and 15% cold coolant returning from
the radiator bottom hose on the other side. This allows
the thermostat to react to the ambient conditions and
provide coolant control for both winter and summer use.
Hot coolant from the engine passes via holes in the
by-pass flow valve into a tube which surrounds 85% of
the thermostat sensitive area. Cold coolant from the
radiator conducts through the remaining 15% of the
sensitive area. In cold ambient conditions, the engine
temperature is raised by approximately 10°C (50°F) to
compensate for the heat loss of 15% exposure to the
cold coolant returning from the bottom hose. This
improves heater performance and engine warm-up.
The by-pass flow valve is held closed by a light spring
and operates to further assists engine and heater
warm-up. When the main valve is closed and the engine
speed is at idle, the coolant pump does not produce
sufficient flow and pressure to overcome the spring and
open the valve. In this condition the valve prevents
coolant circulating through the by-pass circuit and
directs coolant through the heater matrix only. This
provides a higher flow of coolant through the heater
matrix improving passenger comfort in cold conditions.
When the engine speed increases above idle, the coolant
pump produces a greater flow and pressure than the
heater circuit can accommodate. The build up of
pressure acts on the flow valve, overcoming the spring
pressure, opening the valve and relieving the pressure
in the heater circuit. The valve then modulates to provide
maximum coolant flow through the heater matrix and
allowing excess coolant to flow into the by-pass circuit
to provide the engines cooling requirements at higher
engine speeds. The thermostat then regulates the flow
through the radiator to maintain the engine at the
optimum temperature. Maximum opening of the
thermostat, and therefore maximum flow through the
radiator, occurs if the coolant temperature reaches 95°C
(203°F).
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							Cooling System Component Layout
Heater hose, in and out1
Connections for rear heater2
Hose, radiator to expansion tank3
Throttle body4
EGR valve5
Bleed screw6
Hose, water outlet to cylinder block7
Water outlet pipe assembly8
Expansion tank9
Hose, heater to thermostat10
Cylinder block11
Water pump12
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							Hose, radiator to thermostat13
Oil cooler14
Cooling fan15
Shroud, lower16
Transmission oil pipes17
Radiator18
Shroud, upper19
Hose, water outlet to radiator20
GENERAL
The cooling system employed is of the pressure relief
by-pass type, which allows coolant to circulate around
the engine and the heater circuit while the thermostat
main valve is closed. The primary function of the
cooling system is to maintain the engine within an
optimum temperature range under changing ambient
and engine operating conditions. Secondary functions
are to provide heating for the passenger compartment
and cooling for the transmission fluid and engine oil.
The cooling system comprises:
•A radiator
•A passenger compartment heater matrix
•A coolant pump
•A thermostat
•An expansion tank
•An electro-viscous fan
•Connecting hoses and pipes.
ENGINE COOLING SYSTEM
The coolant is circulated by a centrifugal pump mounted
on the front of the engine and driven by an ancillary
drive polyvee belt. The coolant pump circulates coolant
through the cylinder block and cylinder heads via a
chamber located in the vee of the engine. Having passed
through the engine the coolant returns to the thermostat
housing. The coolant then progresses down the top hose
to the heater pipe. The heater pipes lead to the bulkhead
and return to the engine side of the thermostat.
The engine contains a normal thermostat which is
positioned such that the waxs temperature is controlled
by both the coolant from the radiator and the bypass.
This results in the thermostat being able to vary its
opening temperature dependant on ambient conditions.
The thermostat housing also contains a sprung loaded
valve, which limits the amount flow using the bypass.
This means that the engine can run without coolant
flowing through the bypass temporarily, to improve
heater performance.
The radiator is a cross flow type with an aluminium
matrix and has a drain tap on the lower right-hand rear
face. The lower radiator mountings are located part way
up the end tanks. The mountings are fitted with rubber
bushes, which sit on the upper chassis rails. The radiator
upper is mounted by pins, which are pushed through
rubber bushes mounted in the Front End Carrier (FEC)
above the radiator. The radiator also incorporates two
connections for the transmission oil pipes.
The top and bottom hoses are mounted to the inlet and
outlet sides of the thermostat housing.
The expansion tank is fitted forward of the LH
suspension turret in the engine compartment. The
expansion tank allows for the expansion of the coolant
as the engine gets hot and also supplies the engine with
coolant as the coolant in the engine contracts. The tank
also allows any air trapped in the coolant to be removed.
The liquid cooled transmission fluid cooler is mounted
in the cold side radiator end tank. It is positioned in the
middle of the LH end tank.
The engine oil cooler (EOC) is feed coolant from the
bottom hose. Coolant is diverted from between the
radiator and the thermostat, directed to the cooler and
then returned to the bottom hose.
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							For additional airflow through the radiator matrix,
particularly when the vehicle is stationary, there is an
engine driven electro-viscous unit. This unit functions
as a normal viscous fan, but with electronic control over
the level engagement of the clutch. The Engine Control
Module (ECM), which determines the required fan
speed, controls the level of clutch engagement. The
ECM determines engagement based on the coolant,
ambient and transmission oil temperatures and air
conditioning (A/C) system pressure. The fan is mounted
using a left hand thread.
The viscous fan unit is electronically controlled by the
ECM to optimise fan speed for all operating conditions.
NOTE: If the electrical connections to the viscous fan
are disconnected the fan will idle and overheating may
result. The ECM stores the appropriate fault codes in
this case.
Engine CoolingLesson 2 – Powertrain
123Technical Training (G421100) 
						

							ENGINE COOLING SYSTEM OPERATION
Cooling System Coolant Flow
(G421100) Technical Training124
Lesson 2 – PowertrainEngine Cooling 
						

							When the engine is running the coolant pump is driven
by the ancillary drive belt. This forces coolant to
circulate around the engine and heater, while the
thermostat and bypass valve are shut. As the temperature
and pressure increases the bypass valve is forced open
allowing coolant to circulate through the bypass valve.
When the temperature reaches 82°C (180°F) the main
thermostat begins to open allowing coolant to circulate
through the main radiator. As the thermostat
progressively opens (fully open at 95°C (203°F)), the
bypass valve progressively closes forcing any coolant
through the heater or radiator. Once coolant is allowed
to circulate through the radiator, the transmission fluid
and the engine oil coolers begin to receive coolant flow.
The increased coolant volume, created by heat
expansion, is directed to the expansion tank through a
bleed hose from the top of the radiator. The expansion
tank has an outlet hose which is connected into the
coolant circuit. This outlet hose returns the coolant to
the system when the engine cools.
Coolant flows through the radiator from the top right
hand tank to the bottom left hand tank and is cooled by
air passing through the matrix. The temperature of the
cooling system is monitored by the ECM via the Engine
Coolant temperature (ECT) sensor located in the
cylinder head. The ECM uses signals from this sensor
to control the cooling fan operation and adjust fuelling
according to engine temperature.
To control the cooling fan, the ECM sends a Pulse
Width Modulated (PWM) signal to the cooling fan
module (integral to the ECM). The frequency of the
PWM signal is used by the cooling fan module to
determine the output voltage supplied to the fan motor.
The ECM varies the duty cycle of the PWM signal
between 0 and 100% to vary the fan speed. If the PWM
signal is outside the 0 to 100% range, the cooling fan
module interprets the signal as an open or short circuit
and runs the fans at maximum speed to ensure the engine
and gearbox do not overheat.
The ECM operates the fan in response to inputs from
the ECT sensor, the transmission oil temperature sensor,
the A/C switch and the A/C pressure sensor.
The speed of the cooling fan is also influenced by
vehicle road speed. The ECM adjusts the speed of the
cooling fans, to compensate for the ram effect of vehicle
speed, using the Controller Area Network (CAN) road
speed signal received from the Anti-lock Braking
System (ABS) module.
Engine CoolingLesson 2 – Powertrain
125Technical Training (G421100) 
						

							Cooling System Component Layout – Manual Gearbox Without Fuel Burning Heater (FBH)
Heater hose, in and out1Heater hose, in and out, for vehicles with rear
heater (optional)
2
(G421101) Technical Training126
Lesson 2 – PowertrainEngine Cooling