1994 JAGUAR XJ6 overheating

Cooling System (AJl6) m
4.1.1 COOLING SYSTEM DESCRIPTION
4.1.1.1 Major Components
o Main engine crossflow radiator, incorporating a concentric tube cooler for the power steering fluid mounted in
the right
-hand radiator side tank. Vehicles with automatic transmission have a transmission fluid cooler
mounted in the left
-hand radiator side tank; for 4,O liter supercharged engines a six-plate cooler is fitted; other
vehicles have
a tube-type cooler. Adouble-action temperature switch, for controlling the radiator cooling fans,
is mounted in the left
-hand radiator side tank.
0 Two electrically operated radiator cooling fans, mounted behind the main radiator.
0 Coolant circulating pump, belt driven from the engine crankshaft.
0 Coolant header tank with pressure relief cap and coolant level probe.
o Engine thermostat.
4.1.1.2
0 Heater matrix.
o Electrically operated coolant circulating pump, mounted on the left-hand side of the engine bulkhead.
o Solenoid operated valve, located adjacent to the coolant circulating pump.
Components for Climate Control System
4.1.1.3 Components for Supercharged Engine
0 0 Supercharger crossflow radiator, mounted in front of the main radiator. The supercharger radiator is reverse- circuited, i.e. the coolant inlet is at the bottom of the radiator.
0 Electrically operated coolant circulating pump, located at the left-hand side of the main radiator.
4.1.1.4 Operation
The configuration of the cooling system for normally aspirated and supercharged (4,O liter) engines is shown in Sub- section 4.1.2.
The cooling system is pressurized, which allows the system to operate at a higher temperature without overheating.
The header tank is fitted with a pressure relief cap to protect the system against overpressure.
Under cold start conditions, coolant is forced by the engine driven water pump through the cylinder block and cylinder
head to the thermostat housing. The thermostat is closed to give rapid engine warm up, hence the coolant is returned
directly to the water pump inlet. When normal engine operating temperature is reached, the thermostat opens and
coolant is diverted through the radiator before returning to the water pump inlet. In vehicles fitted with
a supercharger,
coolant is circulated through the supercharger radiator and intercooler by the supercharger water pump. The super- charger cooling circuit uses the same coolant header tank as the main engine cooling system.
The radiator cooling fans operate in series and parallel under the control of the double
-action radiator mounted tem- perature switch. The fans are also controlled by the climate control system on vehicles fitted with air conditioning.
Under hot operating conditions, the fans may continue to operate after the engine has been switched off. The fans
stop automatically when the coolant temperature has been reduced sufficiently.
The system also provides the coolant supply for the climate control system, which is described in Section
14.
X300 VSM 1 Issue 1 August 1994

Cooling System (V12
4.2.1 COOLING SYSTEM DESCRIPTION I
4.2.1.1 Major Components
o Engine crossflow radiator, incorporating a concentric tube cooler for the power steering fluid mounted in the
left
-hand radiator side tank. Vehicles with automatic transmission have a six-plate transmission fluid cooler
mounted in the right
-hand radiator side tank. A double-action temperature switch, for controlling the electric
radiator cooling fans, is mounted in the left
-hand radiator side tank.
0 Engine driven, viscous-coupled, radiator cooling fan
0 Two electrically operated radiator cooling fans, mounted in front of the radiator.
o Coolant circulating pump, belt driven from the engine crankshaft.
0 Coolant header tank with pressure relief cap and coolant level probe.
0 Two engine thermostats, one in each cylinder bank.
4.2.1.2
0 Heater matrix.
0 Electrically operated coolant circulating pump, mounted on the left-hand side of the engine bulkhead.
o Solenoid operated valve, located adjacent to the coolant circulating pump.
Components for Climate Control System
1
4.2.1.3 Operation
The configuration of the cooling system is shown in Sub-section 4.2.2.
The cooling system is pressurized, which allows the system to operate at a higher temperature without overheating.
The header tank is fitted with a pressure relief cap to protect the system against overpressure.
Under cold start conditions, coolant is forced by the engine driven water pump through each cylinder block and cylin
- der head to the thermostat housings. The thermostats are closed to give rapid engine warm up, hence the coolant is
returned via the engine cross pipe to the water pump inlet. When normal engine operating temperature is reached,
the thermostats open and coolant is diverted through the radiator before returning to the water pump inlet.
If the engine driven fan is unable to provide sufficient cooling, the electrically operated fans operate in series and paral
-
lel underthe control of the radiator mounted temperature switch. Under hot operating conditions, the electric fans may
continue to operate after the engine has been switched off. The fans stop automatically when the coolant temperature
has been reduced sufficiently.
The system also provides the coolant supply for the climate control system, which is described in Section 14.
I
I X300 VSM 1 Issue 1 August 1994

4.2.5.2 Diagnostic Procedures
1
I Symptom ..
Overheating
herheating at
dle
roo cold ~~~
Possible Cause
Thermostat(s) stuck
closed
Incorrect thermostat rating
Faulty temperature gauge
Faulty temperature transmitter
Radiator core blocked
Radiator grille obstructed
Concentration of anti
-freeze
too high
Drive belt slack
Drive belt broken
Water pump seized
lnsuff icient coolant
Internally collapsed hoses
Incorrect ignition timing
Fuel
/ air mixture too weak
Incorrect valve timing
Cylinder head
gasket(s) leak-
ing
Brakes binding
Electric cooling
fan(s) not op- erating
Thermostat(s) stuck open
Incorrect thermostat rating
Thermostatb) not fitted
Electric cooling
fan(s) operat-
ing continuously
Faulty temperature gauge
Faulty temperature transmitter
Check
Cooling System (V12)
4.2.5 FAULT DIAGNOSIS
4.2.5.1 Introduction
The following diagnostic procedures are provided to assist properly qualified persons to identify and rectify the faults in the system which are most likely to be encountered. Reference is made to the Electrical Diagnostic Manual (EDM), which should be consulted for all electrical faults. When investigating faults relating to temperature, the prevailing
ambient temperature conditions should be taken into account. The climate control system is dealt with in Section 14.
Test thermostat(s)
Check thermostat operating
temperature
Refer to EDM
Refer to EDM
Check for
hotspots in radiator
Check grille for obstruction
Check strength of coolant
Check belt tension
Visual check Slacken drive belt and turn
water pump pulley by hand.
Check belt for damage
Check coolant level
Pressure test system and
check for deformation of hoses
Refer to EDM
Refer to EDM
Check valve timing
Pressure
-test system. (Check
for contamination of coolant in
header tank)
Check brake calipers for stick
- ing pistons and seized brake
pad pins
..
Refer to EDM
Test
thermostat(4
Check thermostat operating
temperature
Remove thermostat housing
and inspect
Refer to EDM
Refer to EDM
Refer to EDM
Remedy
Renew thermostat(s)
Renew thermostat(s1
Renew gauge
Renew transmitter
Flush or renew radiator
Remove obstruction from
grille
Drain and
fill with coolant of
correct concentration
Adjust belt to correct tension
or renew belt
if worn
Renew belt
Renew water pump. Renew
drive belt
if required
Top
-up coolant
Renew hoses as required
Rectify as required
Rectify as required
Correct valve timing
Renew head
gasket(s)
Rectify as required
Rectify as required
Renew
thermostat(s1
Renew thermostatb)
Fit thermostat(s)
Rectify as required
Renew gauge
Renew transmitter
Issue 1 August 1994 X300 VSM 5

General Fitting Instructions
J51 051
A3.3 TAPER ROLLER BEARINGS,
FAULT DIAGNOSIS
I
Fault
Bent cage.
Cause
Improper handling or use of tool.
Remedy
Renew the bearing.
Fault
Bent cage.
Cause
Improper handling or use of tool.
Remedy
Renew the bearing.
Fault
Galling.
Cause
Marks on roller ends due to overheating, lubricant failure or
overloading.
Remedy
Renew the bearing. Check the seals and ensure that the
bearing is properly lubricated.
Fault
Step wear.
Cause
Wear on the roller ends caused by fine abrasives.
Remedy
Clean all components and housings. Check the seals and
bearings, and renew if leaking, rough or noisy.
Fault
Fretting.
Cause
Corrosion caused by small movement of components with
no lubrication.
Remedy
Renew the bearing. Check the seals for leakage and ensure
that there is adequate lubrication.
J51 050
J51 052
X300 VSM Issue 1 August 1994 8

General Fitting Instructions
I
Fault
Roller wear.
Cause
Marks on track and rollers caused by fine abrasives.
Remedy
Clean all components and housings. Check the seals and
bearings, and renew if leaking, rough or noisy.
Fault
Cracked race.
Cause
Race cracked due to incorrect fitting to shaft, tipping or poor
seating.
Remedy
Renew the bearing and check the condition of the seals.
Fault
Discolouration.
Cause
Discolouration ranging from black to light brown caused by
moisture or incorrect use of lubricants.
Remedy
Reuse bearings if stains can be removed by light polishing
or if no evidence of overheating is apparent. Checkthe seals
and other component part condition. Renew as necessary.
51 060
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....... ........ e L. U
1
Fault
Discolouration.
Cause
Heat discolouration ranging from blue to faint yellow,
resulting from overload or incorrect lubricant. As excessive
heat can cause softening of tracks and rollers, check by
drawing a fine
file over a softened area. If faulty, the file will
grab and cut metal. If still hard, the file will skid over the
surface without removing any material.
Remedy
Renewthe bearings and seals if any heat damage is evident.
51 062
Issue 1 August 1994 X300 VSM 10

6 Fault
Seizure.
Cause
Seizure caused by lack of lubrication, excessive loads or the
ingress of foreign matter.
Remedy
Renew the bearings. Check the seals for wear and ensure
that there is adequate lubrication.
Fault
Etching.
Cause
The bearing surfaces are grey or greyish black, with the
rollers and track material being etched away. This is usually
related to uneven spacing of the rollers.
Remedy - Renew the bearings. Check the seals for wear and ensure
that there is adequate lubrication.
Fault
Rotating track and inner race material removal.
Cause
Removal of material due to slippage. This can be caused by
poor fit, incorrect lubrication, overheating, overloading and
poor assembly.
Remedy
Renew the bearings and clean all related parts. Check the fit
and ensure the replacement bearings are the correct type.
Renew the shaft or housing if damaged.
J51 OS6
Issue 1 August 1994 11 X300 VSM