1999 LAND ROVER DISCOVERY oil temperature

ENGINE MANAGEMENT SYSTEM - V8
DESCRIPTION AND OPERATION 18-2-51
Conditions
The ECM calculates ignition timing using input from the following:
lCKP sensor.
lKnock sensors (KS).
lMAF sensor.
lTP sensor (idle only).
lECT sensor.
Function
At engine start up, the ECM sets ignition timing dependent on ECT information and starting rev/min from the CKP. As
the running characteristics of the engine change, the ignition timing changes. The ECM compares the CKP signal to
stored values in its memory, and if necessary advances or retards the spark via the ignition coils.
Ignition timing is used by the ECM for knock control.
Knock control
The ECM uses active knock control to prevent possible engine damage due to pre-ignition. This is achieved by
converting engine block noise into a suitable electrical signal that can be processed by the ECM. A major contributing
factor to engine 'knock' is fuel quality, the ECM can function satisfactorily on 91 RON fuel as well as the 95 RON fuel
that it is calibrated for.
Conditions
The ECM knock control system operates as follows:
lHot running engine.
l91 or 95 RON fuel.
Function
The ECM knock control uses two sensors located one between the centre two cylinders of each bank. The knock
sensors consist of piezo ceramic crystals that oscillate to create a voltage signal. During pre-ignition, the frequency
of crystal oscillation increases which alters the signal output to the ECM.
If the knock sensors detect pre-ignition in any of the cylinders, the ECM retards the ignition timing by 3° for that
particular cylinder. If this action stops the engine knock, the ignition timing is restored to its previous figure in
increments of 0.75°. If this action does not stop engine knock then the ECM retards the ignition timing a further 3° up
to a maximum of -15° and then restores it by 0.75° and so on until the engine knock is eliminated.
The ECM also counteracts engine knock at high intake air temperatures by retarding the ignition as above. The ECM
uses the IAT signal to determine air temperature.
Idle speed control
The ECM regulates the engine speed at idling. The ECM uses the idle air control valve (IACV) to compensate for the
idle speed drop that occurs when the engine is placed under greater load than usual. When the throttle is in the rest
position i.e. it has not been pressed, the majority of intake air that the engine consumes comes from the idle air control
valve.
IACV control idle speed
Conditions in which the ECM operates the IACV control idle speed is as follows:
lIf any automatic transmission gears other than P or N are selected.
lIf air conditioning is switched on.
lIf cooling fans are switched on.
lAny electrical loads activated by the driver.
Function
The idle air control valve utilises two coils that use opposing pulse width modulated (PWM) signals to control the
position of a rotary valve. If one of the circuits that supplies the PWM signal fails, the ECM closes down the remaining
signal preventing the idle air control valve from working at its maximum/ minimum setting. If this should occur, the idle
air control valve assumes a default idle position at which the engine idle speed is raised to 1200 rev/min with no load
placed on the engine.

ENGINE MANAGEMENT SYSTEM - V8
18-2-84 REPAIRS
Sensor - radiator temperature
$% 18.30.20
Remove
1.Disconnect battery earth lead.
2.Position container to collect coolant spillage.
3.Disconnect multiplug from sensor.
4.Remove sensor and discard sealing washer.
Refit
1.Fit new sealing washer to sensor.
2.Fit and tighten sensor.
3.Connect multiplug to sensor.
4.Refill cooling system.
5.Connect battery earth lead.
Sensor - camshaft position (CMP)
$% 18.30.24
Remove
1.Release fixings and remove battery cover.
2.Disconnect battery earth lead.
3.Raise front of vehicle.
WARNING: Do not work on or under a
vehicle supported only by a jack. Always
support the vehicle on safety stands.
4.Release fixings and remove underbelly panel.
5.Remove engine oil filter.

+ ENGINE - V8, REPAIRS, Filter - oil.
6.Disconnect engine harness from CMP sensor
and release CMP sensor multiplug from
bracket.
7.Remove bolt from clamp securing CMP sensor
to timing gear cover.
8.Remove clamp and CMP sensor. Discard 'O'
ring from CMP sensor.
Refit
1.Ensure CMP sensor is clean, fit new 'O' ring
and sensor to cover.
2.Fit clamp to CMP sensor and tighten bolt to 8
Nm (6 lbf.ft).
3.Fit sensor multiplug to bracket and connect
engine harness to multiplug.
4.Fit engine oil filter.

+ ENGINE - V8, REPAIRS, Filter - oil.
5.Fit underbelly panel and secure with fixings.
6.Lower vehicle and connect battery earth lead.
7.Fit battery cover and secure with fixings.

COOLING SYSTEM - V8
26-2-6 DESCRIPTION AND OPERATION
Description
General
The cooling system used on the V8 engine is a pressure relief by-pass type system which allows coolant to circulate
around the cylinder block and the heater circuit when the thermostat is closed. With coolant not passing through the
radiator, this promotes faster heater warm-up which in turn improves passenger comfort.
A coolant pump is located in a housing at the front of the engine and is driven by a drive belt. The pump is connected
into the coolant passages cast in the cylinder block and pumps coolant from the radiator through the cylinder block.
A viscous fan is attached by means of a nut to the coolant pump pulley drive spindle. The fan draws air through the
radiator to assist in cooling when the vehicle is stationary. The fan rotational speed is controlled relative to the running
temperature of the engine by a thermostatic valve regulated by a bi-metallic coil.
The cooling system uses a 50/50 mix of anti-freeze and water.
Thermostat housing
A plastic thermostat housing is located behind the radiator. The housing has three connections which locate the
radiator bottom hose, top hose and coolant pump feed hose. The housing contains a wax element and a spring loaded
by-pass flow valve.
Thermostat - Main valve
The thermostat is used to maintain the coolant at the optimum temperature for efficient combustion and to aid engine
warm-up. The thermostat is closed at temperatures below approximately 82°C (179°F). When the coolant
temperature reaches approximately 82°C the thermostat starts to open and is fully open at approximately 96°C
(204°F). In this condition the full flow of coolant is directed through the radiator.
The thermostat is exposed to 90% hot coolant from the engine on one side and 10% cold coolant returning from the
radiator bottom hose on the other side.
Hot coolant from the engine passes from the by-pass pipe through four sensing holes in the flow valve into a tube
surrounding 90% of the thermostat sensitive area. Cold coolant returning from the engine, cooled by the radiator,
conducts through 10% of the sensitive area.
In cold ambient temperatures, the engine temperature is raised by approximately 10°C (50°F) to compensate for the
heat loss of 10% exposure to the cold coolant returning from the bottom hose.
By-pass flow valve
The by-pass flow valve is held closed by a light spring. It operates to further aid 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 open the
valve. In this condition the valve prevents coolant circulating through the by-pass circuit and forces the coolant through
the heater matrix only. This provides a higher flow of coolant through the heater matrix to improve 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 take. The pressure acts on the flow valve and overcomes the valve spring pressure, opening the valve and
limiting the pressure in the heater circuit. The valve modulates to provide maximum coolant flow through the heater
matrix and yet allowing excess coolant to flow into the by-pass circuit to provide the engine's cooling needs at higher
engine rev/min.

COOLING SYSTEM - V8
DESCRIPTION AND OPERATION 26-2-7
Inlet manifold - Cooling connections
Coolant leaves the cylinder block via an outlet pipe attached to the front of the air intake manifold. The pipe is
connected to the thermostat housing and the radiator by a branch hose off the radiator top hose.
Hot coolant from the engine is also directed from the inlet manifold via pipes and hoses into the heater matrix. Coolant
is circulated through the heater matrix at all times when the engine is running.
A further tapping from the inlet manifold supplies coolant to the throttle housing via a hose. The coolant circulates
through a plate attached to the bottom of the housing and is returned through a plastic bleed pipe to an expansion
tank. The hot coolant heats the air intake of the throttle housing preventing ice from forming.
An Engine Coolant Temperature (ECT) sensor is fitted in the inlet manifold adjacent to the manifold outlet pipe. The
sensor monitors coolant temperature emerging from the engine and sends signals to the ECM for engine
management and temperature gauge operation.

+ ENGINE MANAGEMENT SYSTEM - V8, DESCRIPTION AND OPERATION, Description - engine
management.
Expansion tank
The expansion tank is located in the engine compartment. The tank is made from moulded plastic and attached to
brackets on the right hand inner wing. A maximum coolant when cold level is moulded onto the tank.
Excess coolant created by heat expansion is returned to the expansion tank from the radiator bleed pipe at the top of
the radiator. An outlet pipe is connected into the pump feed hose and replaces the coolant displaced by heat
expansion into the system when the engine is cool.
The expansion tank is fitted with a sealed pressure cap. The cap contains a pressure relief valve which opens to allow
excessive pressure and coolant to vent through the overflow pipe. The relief valve opens at a pressure of 1.4 bar (20
lbf.in
2) and above.
Heater matrix
The heater matrix is fitted in the heater assembly inside the passenger compartment. Two pipes pass through the
bulkhead into the engine compartment and provide coolant flow to and from the matrix. The pipes from the bulkhead
are connected to the matrix, sealed with 'O' rings and clamped with circular rings.
The matrix is constructed from aluminium with two end tanks interconnected with tubes. Aluminium fins are located
between the tubes and conduct heat away from the hot coolant flowing through the tubes. Air from the heater
assembly is warmed as it passes through the matrix fins. The warm air is then distributed into the passenger
compartment as required.

+ HEATING AND VENTILATION, DESCRIPTION AND OPERATION, Description.When the engine is
running, coolant from the engine is constantly circulated through the heater matrix.
Radiator
The 45 row radiator is located at the front of the vehicle. The cross-flow type radiator is manufactured from aluminium
with moulded plastic end tanks interconnected with tubes. Aluminium fins are located between the tubes and conduct
heat from the hot coolant flowing through the tubes, reducing the cooling temperature as it flows through the radiator.
Air intake from the front of the vehicle when moving carries heat away from the fins. When the vehicle is stationary,
the viscous fan draws air through the radiator fins to prevent the engine from overheating.
Two connections at the top of the radiator provide for the attachment of the top hose and bleed pipe. A connection at
the bottom of the radiator allows for the attachment of the bottom hose to the thermostat housing.
Two smaller radiators are located in front of the cooling radiator. The lower radiator provides cooling of the gearbox
oil and the upper radiator provides cooling for the engine oil.

+ MANUAL GEARBOX - R380, DESCRIPTION AND OPERATION, Description.

+ AUTOMATIC GEARBOX - ZF4HP22 - 24, DESCRIPTION AND OPERATION, Description.

+ ENGINE - V8, DESCRIPTION AND OPERATION, Description.
Pipes and hoses
The coolant circuit comprises flexible hoses and metal formed pipes which direct coolant into and out of the engine,
radiator and heater matrix. Plastic pipes are used for the bleed and overflow pipes to the expansion tank.
A bleed screw is installed in the radiator top hose and is used to bleed air during system filling. A drain plug is fitted
to each cylinder bank in the cylinder block. These are used to drain the block of coolant.

COOLING SYSTEM - V8
DESCRIPTION AND OPERATION 26-2-9
Viscous fan
1Coolant pump pulley drive attachment
2Fan blades3Bi-metallic coil
4Body
The viscous fan provides a means of controlling the speed of the fan relative to the operating temperature of the
engine. The fan rotation draws air through the radiator, reducing engine coolant temperatures when the vehicle is
stationary or moving slowly.
The viscous fan is attached to the coolant pump drive pulley and secured to the pulley by a nut. The nut is positively
attached to a spindle which is supported on bearings in the fan body. The viscous drive comprises a circular drive
plate attached to the spindle and driven from the coolant pump pulley and the coupling body. The drive plate and the
body have interlocking annular grooves with a small clearance which provides the drive when silicone fluid enters the
fluid chamber. A bi-metallic coil is fitted externally on the forward face of the body. The coil is connected to and
operates a valve in the body. The valve operates on a valve plate with ports that connect the reservoir to the fluid
chamber. The valve plate also has return ports which, when the valve is closed, scoop fluid from the fluid chamber
and push it into the reservoir under centrifugal force.
Silicone fluid is retained in a reservoir at the front of the body. When the engine is off and the fan is stationary, the
silicone fluid level stabilises between the reservoir and the fluid chamber. This will result in the fan operating when the
engine is started, but the drive will be removed quickly after the fan starts rotating and the fan will 'freewheel'.
At low radiator temperatures, the fan operation is not required and the bi-metallic coil keeps the valve closed,
separating the silicone fluid from the drive plate. This allows the fan to 'freewheel' reducing the load on the engine,
improving fuel consumption and reducing noise generated by the rotation of the fan.
When the radiator temperature increases, the bi-metallic coil reacts and moves the valve, allowing the silicone fluid
to flow into the fluid chamber. The resistance to shear of the silicone fluid creates drag on the drive plate and provides
drive to the body and the fan blades.

COOLING SYSTEM - V8
DESCRIPTION AND OPERATION 26-2-11
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 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.
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 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 cause 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 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 - V8
26-2-16 REPAIRS
8.Remove 6 scrivets and remove LH and RH air
deflectors from front panel. Disconnect
multiplug of gearbox oil temperature sensor
(arrowed).
9.Remove nut and move horn aside. 10.Remove 2 bolts securing radiator LH and RH
upper mounting brackets to body panel and
remove brackets.
11.Remove 4 screws securing air conditioning
condenser LH and RH upper mounting
brackets to condenser.
12.Remove brackets with rubber mounts from
radiator extension brackets.
13.Position absorbent cloth under each cooler
hose to collect oil spillage.
14.Push against coupling release rings and
disconnect hoses from gearbox oil cooler.
CAUTION: Always fit plugs to open
connections to prevent contamination.
15. If fitted: Push against coupling release rings
and disconnect hoses from engine oil cooler.

COOLING SYSTEM - V8
REPAIRS 26-2-17
16.Remove radiator assembly.
17.Release clip and remove bottom hose from
radiator.
18.Remove 2 bolts and remove extension
brackets from radiator.
19.Remove 2 captive nuts from radiator.
20.Remove 2 screws and remove gearbox oil
cooler from radiator.
21. If fitted: Remove 2 screws and remove engine
oil cooler from radiator.
22.Remove 2 rubber mountings from radiator.
23.Remove sealing strip from bottom of radiator.
24.Remove 2 cowl retaining clips from radiator. Refit
1.Fit cowl retaining clips to radiator.
2.Fit sealing strip to radiator.
3.Fit rubber mountings to radiator.
4.Fit gearbox oil cooler to radiator and secure
with screws.
5. If fitted: Fit engine oil cooler to radiator and
secure with screws.
6.Fit captive nuts to radiator.
7.Fit extension brackets to radiator and secure
with bolts.
8.Fit bottom hose to radiator and secure with clip.
9.Fit radiator and engage lower mountings in
chassis.
10.Ensure connections are clean, then secure
hoses to oil coolers.
11.Fit air conditioning condenser brackets and
secure with screws.
12.Fit radiator upper mounting brackets and
secure with bolts.
13.Fit LH horn and secure with nut.
14.Fit air deflectors and secure with scrivets.
15.Connect multiplug of gearbox oil temperature
sensor.
16.Fit front grille.

+ EXTERIOR FITTINGS, REPAIRS,
Grille - front - up to 03MY.
17.Connect bottom hose to thermostat housing
and secure with clip.
18.Connect top hose to radiator and secure with
clip.
19.Connect bleed hose to radiator and fit clip.
20.Fit lower fan cowl and secure with screws.
21.Fit viscous fan.

+ COOLING SYSTEM - V8, REPAIRS,
Fan - viscous.
22.Top up gearbox oil.
23.Top up engine oil.
24.Refill cooling system.

+ COOLING SYSTEM - V8,
ADJUSTMENTS, Drain and refill.