1999 JAGUAR S TYPE cooling

V6 Engine AJ-V6/AJ28
36
Fail Safe Cooling System
A unique feature of the V6 engine is the use of a fail safe cooling strategy, controlled by the EMS, in the
event of coolant loss leading to rising engine temperatures. The principle of the strategy involves
switching off one or more fuel injectors to inhibit combustion and reduce heat, thus allowing the flow of
ambient intake air to further cool the selected cylinders. By cycling the selected cylinders, ie switching
different injectors off for a period and in a sequence determined by EMS parameters, overall engine
temperature can be controlled sufficiently to allow the vehicle to be driven, at reduced power, for a
short distance. Throughout the malfunction period, instrument panel messages and warnings advise the
driver of the current status of the cooling system as described below.
Driver Indication and EMS Action
The fail safe strategy moves though different stages depending on engine temperature:
¥ Temperatures below 122û C (250û F) are within the normal range. At high temperatures below this
level the temperature gauge pointer enters the red zone.
¥ If the temperature rises to between 122û C - 127û C (250û F to 260û F) no action is taken by the EMS
which affects engine running but the following indications appear:
Temperature gauge pointer in red zone
Message Centre HIGH ENGINE TEMPERATURE
Warning light TEMP
Priority light red
Audible indicator single chime sounded
¥ If the temperature rises to 127û C (260û F) or above, the fail safe strategy operates. At 127û C (260û F),
the EMS will cut out one cylinder (the selected cylinder is varied) and as the temperature continues
to rise, this will increase to a maximum of three cylinders cut (with cylinder cycling). The following
indications are given:
Temperature gauge pointer in red zone
Message Centre ENGINE POWER REDUCED
Warning light TEMP
Priority light red
Audible indicator three chimes sounded
¥ At 166û C (300û F) or above, the fail safe strategy continues as described but the following
indications are given:
Temperature gauge pointer in red zone
Message Centre PULL OFF ROAD SAFELY alternates with TURN OFF IGNITION
Warning light TEMP flashes
Priority light red
Audible indicator five chimes sounded
¥ EMS shuts the engine down.

V6 Engine AJ-V6/AJ28
40
Engine Management Sensors
Key to illustration on page 41:
1. Throttle motor
2. TP sensor
3. IAT sensor
4. MAF sensor
5. Top IMT valve
6. Bottom IMT valve
7. EFT sensor
8. IP sensor
9. Fuel injectors
10. Coil-on-plug units
11. VVT shuttle valve
12. CMP sensor
13. CHT sensor
14. KS sensors
15. EOT sensor
16. CKP sensor
17. HO2 sensors
18. HO2 sensors (catalyst monitors)
Cylinder Head Temperature (CHT) Sensor
The single CHT sensor is located between the two
rear coil-on-plug units in the bank 2 cylinder
head. The sensor directly monitors the metal
temperature of the cylinder head. This method of
engine heat sensing is used in place of a
conventional coolant temperature sensor to
enable the fail safe cooling strategy to operate.
The use of a metal temperature sensor allows
cylinder head temperature to be measured even if
coolant has been lost unlike an ECT sensor which
would produce inaccurate temperature
indications, eg measuring steam temperature.
Crankshaft Position (CKP) Sensor
Crankshaft position and rotational speed are
sensed from a steel timing ring keyed to the front
end of the crankshaft immediately behind the
front cover. The timing ring has 36-1 teeth, ie one
missing tooth, which are angled slightly forward
and bent at rightangles to provide a sensing area
for the inductive sensor. The sensor is positioned
in the front cover, to the side of the crankshaft
damper, at approximately 20û to the plane of the
timing ring.
D.303.1342
J.303.1343
CHT SENSOR
CKP SENSOR
D.303-1342
J.303-1343
Engine management sensors and actuators (but
not off engine sensors) are summarised in the
illustration on page 41 and are also described
below or in the relevant section (VVT, fuel system,
throttle, tuned manifold).
The engine management system is described in a
separate section.

V8 EngineAJ-V6/AJ28
47
Cylinder Head
The cylinder head incorporates the modifications
first introduced for the AJ27 engine except for the
camshaft sensor ring and cam cover.
Camshaft Sensor Ring
Cam position sensing is similar to that used on the
AJ27 engine, except that the sensor ring fitted to
each inlet camshaft has five triggering teeth.
Camshaft Covers
To improve accessibility, an extension tube is
fitted to the oil filler hole on the bank 2 cam
cover. Due to the position of the throttle and air
intake ducting, the part load breather outlet is
taken from bank 1 cam cover and the full load
breather outlet from bank 2 (the reverse of AJ27).
Front Cover
The front cover is modified from the AJ27 to
include a mounting boss for a new idler pulley
(see Front End Accessories Drive).
Lubrication
The lubrication system includes the uprated oil
pump (for the linear VVT system) and the same oil
temperature sensor as fitted to the AJ27 engine.
The oil sump and pan are modified as described
on page 46.
The external oil system components are located
laterally across the front of the sump body and
consist of an oil filter, oil cooler and oil filter head
assembly. The oil cooler is an oil to water heat
exchanger similar to the V6 oil cooler and the
cooler matrix is also connected via hoses to a
circulator orifice in the radiator bottom hose (see
Cooling System). The oil filter screws on to the
cooler which connects to the sump body through
an adaptor, the oil filter head assembly.
J.303.1189
CAMSHAFT SENSOR RING
D.303.1189
D.303.1185
CAMSHAFT COVER/OIL FILLER
D.303.1185
D.303.1186
OIL FILTER, COOLER AND ADAPTOR
D.303.1185
Oil temperature sensor
Oil pressure switch
Oil Cooler

V8 EngineAJ-V6/AJ28
49
Cooling System
The AJ28 engine retains the same basic cooling
system as the previous V8 engines but shares the
radiator, fan shroud assembly, de-gas circuit and
bottom hose oil cooler circulator features with the
V6. The coolant specified for the V6 is also
applicable to the V8 engine.
Particular features of the AJ28 cooling system are:
¥ The thermostat is located in the engine
mounted housing as in previous V8 engines.
¥ The thermostat housing is modified with an
extra stub pipe for the new heater returnhose.
¥ The throttle adaptor is heated from the main
cooling system to provide throttle de-icing.
¥ Both heater hoses, feed and return, are now
routed forward to the heater control valve.
¥ An electric pump is fitted in the heater
coolant circuit (ÔS-TYPE IntroductionÕ
Technical Guide).
¥ The coolant reservoir (de-gas bottle) is fitted
with a level sensor which provides a low level
warning on the instrument panel message
J.303.1366
V8 ENGINE COOLING SYSTEM
1. Radiator
2. Top hose
3. Bottom hose
4. Thermostat
5. Coolant pump6. Engine oil cooler
7. Reservoir bottle
8. Electronic throttle
9. V8 engine
10. AC/heater pump
110512
9
4
6
2
3
8
7
J.303.1365
11
13
11. Heater control valve
12. AC/heater unit
13. Bleed

V8 Engine AJ-V6/AJ28
50centre if the coolant level drops.
¥ The fail safe cooling strategy described for the
V6 is not applicable to the AJ28 engine.
Cooling System Hoses
The cooling system hoses are constructed of the
same materials and have the same type of fittings
as the V6 engine.
D.303.1370
J.303.1388
COOLING SYSTEM HOSES - TOP
J.303.1388
COOLING SYSTEM HOSES - FRONT
D.303.1370
Top Hose
Bottom Hose
A/C Heater
Pump
Heater Control
Valve
Engine Oil Cooler
To A/C Heater
Pump
Throttle
De-icing

V8 EngineAJ-V6/AJ28
51
Air Induction System
Charge air is supplied to the cylinders via an air
cleaner, induction tube, throttle body, throttle
body adaptor and induction manifold.
The throttle body and system operation is
identical to that of the V6 engine.
Induction Manifold
(see illustration on page 52)
To accommodate the V8 engine in the S-TYPE
model, the throttle body is re-located and now
supplies charge air via an inlet at the top centre of
the induction manifold. The manifold is
manufactured from a plastic material and has an
integral injector air supply tube on each side with
holes for the fuel injectors, but as on the AJ27
engine, the fuel feed pipes are not incorporated
into the manifold (see Fuel System). Two stub
pipes at the top of the manifold provide vacuum
connections for the vacuum hose and the brake
servo hose.
A polypropylene covered foam noise isolation pad
fits between the manifold assembly and the block.Throttle Adaptor
The throttle body is mounted to the induction
manifold via a cast aluminium adaptor. The
throttle body adaptor provides input ports for the
evaporative emissions (top stub) and part load
breather (lower side stub) and also mounts the air
assisted injection control (AAC) valve. Input and
output ports for the side mounted AAC valve are
an integral part of the adaptor casting (the ports
do not connect to the induction airstream).
Throttle de-icing is achieved by a coolant feed
through the base of the adaptor instead of the
throttle body itself as on the V6 engine (see
cooling section).
D.303.1278
AIR INDUCTION LAYOUT
D.303.1278
Air Cleaner
Induction Tube
MAF SensorIAT Sensor
Throttle Body
Throttle Body Adaptor

Automatic TransmissionAJ-V6/AJ28
63 controlled solenoid are mounted on an
integral, replaceable, control module
¥ three speed sensors mounted on the external
casing: turbine speed sensor, intermediate
speed sensor and output speed sensor
¥ an oil temperature sensor is fitted inside the
transmission.
The gear select lever is connected via a Bowden
cable to an operating lever on the left side of the
transmission casing. A digital rotary switch, the
transmission range switch, fits over the shaft of
the operating lever and is fixed by two bolts to
the transmission casing. Selection of a particular
drive function generates a 4 bit binary coded
signal which is transmitted directly to the PCM
over a four wire parallel interface. As on the XK
and XJ Series, lateral movement of the gear select
lever across the gate, D to 4 or 4 to D, operates a
switch which indicates the selected function to
the PCM (the Bowden cable is not actuated
laterally).
The PCM directly controls the transmission
actuators as a response to driver demand, engine
requirements and according to the selected shift
mode. Gear selection is controlled by commands
to the four shift solenoids. If, during gear
selection, the relative speeds monitored by the
speed sensors are not as expected, the PCM
varies the analogue signal to the variable force
solenoids to increase/decrease the clutch pressure
(closed loop control). Increased engagement times
due to ageing are also controlled by adaptive shiftpressure.
Apart from the sports mode and traction mode
selected by the driver, there are pre-programmed
modes selected by the PCM in response to sensed
driving conditions :
¥ increased load such as gradients and trailer
towing
¥ cruise control
¥ hot mode: strategies including clutch lock up
are applied to reduce heat.
Transmission Oil Cooler
The transmission fluid is cooled externally by a
dedicated oil to air radiator which is mounted in
the integral cooling pack between the engine
radiator and A/C condenser and below the PAS
cooler.
D.307.320
TRANSMISSION OIL COOLING
Transmission
Oil Cooler
D.307.320