1997 JAGUAR XJ6 radiator cap

3261 Jaguar XJ6
Safety first!0•5
Working on your car can be dangerous.
This page shows just some of the potential
risks and hazards, with the aim of creating a
safety-conscious attitude.
General hazards
Scalding
• Don’t remove the radiator or expansion
tank cap while the engine is hot.
• Engine oil, automatic transmission fluid or
power steering fluid may also be dangerously
hot if the engine has recently been running.
Burning
• Beware of burns from the exhaust system
and from any part of the engine. Brake discs
and drums can also be extremely hot
immediately after use.
Crushing
• When working under or near
a raised vehicle,
always
supplement the
jack with axle
stands, or use
drive-on
ramps.
Never
venture
under a car which
is only supported by a jack.
• Take care if loosening or tightening high-
torque nuts when the vehicle is on stands.
Initial loosening and final tightening should
be done with the wheels on the ground.
Fire
• Fuel is highly flammable; fuel vapour is
explosive.
• Don’t let fuel spill onto a hot engine.
• Do not smoke or allow naked lights
(including pilot lights) anywhere near a
vehicle being worked on. Also beware of
creating sparks
(electrically or by use of tools).
• Fuel vapour is heavier than air, so don’t
work on the fuel system with the vehicle over
an inspection pit.
• Another cause of fire is an electrical
overload or short-circuit. Take care when
repairing or modifying the vehicle wiring.
• Keep a fire extinguisher handy, of a type
suitable for use on fuel and electrical fires.
Electric shock
• Ignition HT
voltage can be
dangerous,
especially to
people with heart
problems or a
pacemaker. Don’t
work on or near the
ignition system with
the engine running or
the ignition switched on.• Mains voltage is also dangerous. Make
sure that any mains-operated equipment is
correctly earthed. Mains power points should
be protected by a residual current device
(RCD) circuit breaker.
Fume or gas intoxication
• Exhaust fumes are
poisonous; they often
contain carbon
monoxide, which is
rapidly fatal if inhaled.
Never run the
engine in a
confined space
such as a garage
with the doors shut.
• Fuel vapour is also
poisonous, as are the vapours from some
cleaning solvents and paint thinners.
Poisonous or irritant substances
• Avoid skin contact with battery acid and
with any fuel, fluid or lubricant, especially
antifreeze, brake hydraulic fluid and Diesel
fuel. Don’t syphon them by mouth. If such a
substance is swallowed or gets into the eyes,
seek medical advice.
• Prolonged contact with used engine oil can
cause skin cancer. Wear gloves or use a
barrier cream if necessary. Change out of oil-
soaked clothes and do not keep oily rags in
your pocket.
• Air conditioning refrigerant forms a
poisonous gas if exposed to a naked flame
(including a cigarette). It can also cause skin
burns on contact.
Asbestos
• Asbestos dust can cause cancer if inhaled
or swallowed. Asbestos may be found in
gaskets and in brake and clutch linings.
When dealing with such components it is
safest to assume that they contain asbestos.
Special hazards
Hydrofluoric acid
• This extremely corrosive acid is formed
when certain types of synthetic rubber, found
in some O-rings, oil seals, fuel hoses etc, are
exposed to temperatures above 400
0C. The
rubber changes into a charred or sticky
substance containing the acid. Once formed,
the acid remains dangerous for years. If it
gets onto the skin, it may be necessary to
amputate the limb concerned.
• When dealing with a vehicle which has
suffered a fire, or with components salvaged
from such a vehicle, wear protective gloves
and discard them after use.
The battery
• Batteries contain sulphuric acid, which
attacks clothing, eyes and skin. Take care
when topping-up or carrying the battery.
• The hydrogen gas given off by the battery
is highly explosive. Never cause a spark or
allow a naked light nearby. Be careful when
connecting and disconnecting battery
chargers or jump leads.
Air bags
• Air bags can cause injury if they go off
accidentally. Take care when removing the
steering wheel and/or facia. Special storage
instructions may apply.
Diesel injection equipment
• Diesel injection pumps supply fuel at very
high pressure. Take care when working on
the fuel injectors and fuel pipes.
Warning: Never expose the hands,
face or any other part of the body
to injector spray; the fuel can
penetrate the skin with potentially fatal
results.
Remember...
DO
• Do use eye protection when using power
tools, and when working under the vehicle.
• Do wear gloves or use barrier cream to
protect your hands when necessary.
• Do get someone to check periodically
that all is well when working alone on the
vehicle.
• Do keep loose clothing and long hair well
out of the way of moving mechanical parts.
• Do remove rings, wristwatch etc, before
working on the vehicle – especially the
electrical system.
• Do ensure that any lifting or jacking
equipment has a safe working load rating
adequate for the job.
A few tips
DON’T
• Don’t attempt to lift a heavy component
which may be beyond your capability – get
assistance.
• Don’t rush to finish a job, or take
unverified short cuts.
• Don’t use ill-fitting tools which may slip
and cause injury.
• Don’t leave tools or parts lying around
where someone can trip over them. Mop
up oil and fuel spills at once.
• Don’t allow children or pets to play in or
near a vehicle being worked on.

3261 Jaguar XJ6
Weekly checks0•11
Engine oil level
Before you start
4Make sure that your car is on level ground.
4Check the oil level before the car is driven,
or at least 5 minutes after the engine has been
switched off.
The correct oilModern engines place great demands on their
oil. It is very important that the correct oil for
your car is used (See “Lubricants, fluids and
tyre pressures”).
Car care
l If you have to add oil frequently, you should
check whether you have any oil leaks. Place
some clean paper under the car overnight,
and check for stains in the morning. If there
are no leaks, the engine may be burning oil
(see “Fault finding”).
lAlways maintain the level between the
upper and lower dipstick marks (see photo 3).
If the level is too low severe engine damage
may occur. Oil seal failure may result if the
engine is overfilled by adding too much oil.
If the oil level is checked
immediately after driving the
vehicle, some of the oil will
remain in the upper engine
components, resulting in an inaccurate
reading on the dipstick!
The dipstick is located at the rear of the
engine on the left-hand side (see “Under-
bonnet check points” on page 0•10 for
exact location). Withdraw the dipstick.Using a clean rag or paper towel remove
all oil from the dipstick. Insert the clean
dipstick into the tube as far as it will go,
then withdraw it again.
Note the oil level on the end of the
dipstick which should be between the
upper and lower marks. The “M” mark is
for use when checking the oil level after the
vehicle has been standing overnight; in this
case the oil level should be between the “M”
and upper level markings.Oil is added through the filler cap.
Unscrew the cap and top-up the level; a
funnel may help to reduce spillage. Add
the oil slowly, checking the level on the dipstick
often. Don’t overfill (see “Car care” left).
12
34
Warning: DO NOT attempt to
remove the expansion tank
pressure cap when the engine
is hot, as there is a very great
risk of scalding. Do not leave
open containers of coolant
about, as it is poisonous.
Car care
lAdding coolant should not be necessary on
a regular basis. If frequent topping-up is
required, it is likely there is a leak. Check the
radiator, all hoses and joint faces for signs of
staining or wetness, and rectify as necessary.
lIt is important that antifreeze is used in the
cooling system all year round, not just during
the winter months. Don’t top-up with water
alone, as the antifreeze will become too
diluted.
Coolant level
The coolant level should be checked only
with the engine cold. The level is checked
in the expansion tank on the left-hand
side of the engine compartment. Remove the
expansion tank pressure cap and check that
the coolant level is upto the base of filler neck.If topping up is necessary, add a mixture
of water and antifreeze to the expansion
tank until the coolant level is upto the
base of the filler neck. Once the level is
correct, securely refit the pressure cap.12

1•4Maintenance - component location
3261 Jaguar XJ6
1 Battery
2 Oil filler cap
3 Engine oil dipstick (not visible)
4 Automatic transmission
dipstick (not visible)
5 Brake fluid reservoir
6 Coolant reservoir
(expansion tank)
7 Air cleaner housing
8 Upper radiator hose
9 Spark plugs
10 Distributor
11 Windscreen washer fluid
reservoir
12 Power hydraulic system fluid
reservoir
13 Power steering fluid reservoir
Underbonnet view from the left-hand side of the vehicle Underbonnet view from the right-hand side of the vehicle
1 Battery
2 Oil filler cap
3 Engine oil dipstick (not visible)
4 Automatic transmission
dipstick (not visible)
5 Brake fluid reservoir
6 Coolant reservoir (expansion
tank)
7 Air cleaner housing
8 Upper radiator hose
9 Spark plugs
10 Distributor
11 Windscreen washer fluid
reservoir
12 Power hydraulic system fluid
reservoir
13 Power steering fluid reservoir

leak be found, renew the offending gasket or
oil seal by referring to the appropriate
Chapters in this manual.
2Also check the security and condition of all
the engine-related pipes and hoses. Ensure
that all cable ties or securing clips are in place
and in good condition. Clips which are broken
or missing can lead to chafing of the hoses,
pipes or wiring, which could cause more
serious problems in the future.
3Carefully check the radiator hoses and
heater hoses along their entire length. Renew
any hose which is cracked, swollen or
deteriorated. Cracks will show up better if
the hose is squeezed. Pay close attention
to the hose clips that secure the hoses to the
cooling system components. Hose clips can
pinch and puncture hoses, resulting in cooling
system leaks.
4Inspect all the cooling system components
(hoses, joint faces etc.) for leaks. A leak in the
cooling system will usually show up as white-
or rust-coloured deposits on the area
adjoining the leak. Where any problems of this
nature are found on system components,
renew the component or gasket with
reference to Chapter 3.
5From within the engine compartment,
check the security of all fuel hose attachments
and pipe unions, and inspect the fuel hoses
and vacuum hoses for kinks, chafing and
deterioration.
6Also check the condition of the power
steering fluid hoses and pipes.
8 Automatic transmission
fluid level check
1
1The level of the automatic transmission fluid
should be carefully maintained. Low fluid level
can lead to slipping or loss of drive, while
overfilling can cause foaming, loss of fluid and
transmission damage.
2The transmission fluid level should only be
checked when the transmission is at its
normal operating temperature.
Caution: If the vehicle has just been driven
for a long time at high speed or in city
traffic in hot weather, or if it has been
pulling a trailer, an accurate fluid level
reading cannot be obtained. Allow the fluid
to cool down for about 30 minutes.
3If the vehicle has not been driven, park the
vehicle on level ground, set the handbrake,
then start the engine and bring it to operating
temperature. While the engine is idling,
depress the brake pedal and move the
selector lever through all the gear ranges,
beginning and ending in Park.
4With the engine still idling, remove the
dipstick from its tube (see illustration). Check
the level of the fluid on the dipstick (see
illustration)and note its condition.
5Wipe the fluid from the dipstick with a clean
rag and reinsert it back into the filler tube until
the cap seats.6Pull the dipstick out again and note the fluid
level. If the transmission is cold, the level
should be in the COLD or COOL range on the
dipstick. If it is hot, the fluid level should be in
the HOT range. If the level is at the low side of
either range, add the specified transmission
fluid through the dipstick tube with a funnel.
7Add just enough of the recommended fluid
to fill the transmission to the proper level. It
takes about one pint to raise the level from the
low mark to the high mark when the fluid is
hot, so add the fluid a little at a time and keep
checking the level until it is correct.
8The condition of the fluid should also be
checked along with the level. If the fluid at the
end of the dipstick is black or a dark reddish
brown colour, or if it emits a burned smell, the
fluid should be changed (see Section 26). If
you are in doubt about the condition of the
fluid, purchase some new fluid and compare
the two for colour and smell.9 Differential oil level check
1
1The differential has a check/fill plug which
must be removed to check the lubricant level.
If the vehicle is raised to gain access to the
plug, be sure to support it safely on axle
stands - DO NOT crawl under the vehicle
when it’s supported only by the jack!2Remove the lubricant check/fill plug from
the differential (see illustration).Use a
3/8-inch drive ratchet and a short extension to
unscrew the plug.
3Use your little finger as a dipstick to make
sure the lubricant level is even with the
bottom of the plug hole. If not, use a syringe
or squeeze bottle to add the recommended
lubricant until it just starts to run out of the
opening.
4Refit the plug and tighten it securely.
10 Exhaust system check
1
1With the engine cold (at least three hours
after the vehicle has been driven), check the
complete exhaust system from its starting
point at the engine to the end of the tailpipe.
This should be done on a hoist where
unrestricted access is available.
2Check the pipes and connections for
evidence of leaks, severe corrosion or
damage. Make sure that all brackets and
hangers are in good condition and tight (see
illustration).
3At the same time, inspect the underside of
the body for holes, corrosion, open seams,
etc. which may allow exhaust gases to enter
the passenger compartment. Seal all body
openings with silicone or body putty.
4Rattles and other noises can often be
traced to the exhaust system, especially the
mounts and hangers. Try to move the pipes,
Every 7500 miles or 6 months 1•11
1
9.2 The differential check/fill plug is
located on the rear of the differential
housing - place your finger in the filler plug
hole to make sure the lubricant level is
even with the bottom of the hole
10.2 Check the exhaust system hangers
(arrowed) for damage and cracks
3261 Jaguar XJ6
8.4a The automatic transmission dipstick
(arrowed) is located in a tube which
extends forward from the transmission
8.4b Check the automatic transmission
fluid with the engine idling at operating
temperature and the gear selector in Park,
then add fluid to bring the level to the
upper mark

30 Coolant renewal
2
Warning: Do not allow engine
coolant (antifreeze) to come in
contact with your skin or painted
surfaces of the vehicle. Rinse off
spills immediately with plenty of water.
Antifreeze is highly toxic if ingested. Never
leave antifreeze laying around in an open
container or in puddles on the floor;
children and pets are attracted by it’s
sweet smell and may drink it. Check with
local authorities about disposing of used
antifreeze. Your local authority may have
collection centres which will see that
antifreeze is disposed of safely.1Periodically, the cooling system should be
drained, flushed and refilled to replenish the
antifreeze mixture and prevent formation of
rust and corrosion, which can impair the
performance of the cooling system and
cause engine damage. When the cooling
system is serviced, all hoses and the radiator
cap should be checked and renewed if
necessary.
Draining
2Apply the handbrake and block the wheels.
If the vehicle has just been driven, wait several
hours to allow the engine to cool down before
beginning this procedure.
3Remove the expansion tank pressure cap
(see illustration).
4Move a large container under the radiator
drain to catch the coolant. Then using a largescrewdriver, open the radiator drain plug and
direct the coolant into the container (see
illustration).
27 Differential oil renewal
2
1Drive the car for several miles to warm up
the differential lubricant, then raise the car
and support it securely on axle stands.
2Move a drain pan, rags, newspapers and
the required tools under the car.
3Remove the check/fill plug from the
differential. If necessary refer to Section 9 for
the check/fill plug location.
4With the drain pan under the differential,
use a ratchet and socket to loosen the drain
plug (see illustration). Note:A special pipe
plug socket may be required to complete this
procedure.
5Once loosened, carefully unscrew it with
your fingers until you can remove it from the
case. Since the lubricant will be hot, wear a
rubber glove to prevent burns.
6Allow all of the oil to drain into the pan, then
replace the drain plug and tighten it securely.
7Refer to Section 9 and fill the differential
with lubricant.
8Refit the fill plug and tighten it securely.
9Lower the vehicle. Check for leaks at the
drain plug after the first few miles of driving.
28 Brake fluid renewal
2
Warning: Brake fluid can harm
your eyes and damage painted
surfaces, so use extreme
caution when handling or
pouring it. Do not use brake fluid that has
been standing open or is more than oneyear old. Brake fluid absorbs moisture from
the air. Excess moisture can cause a
dangerous loss of braking effectiveness.
1At the specified time intervals, the brake
fluid should be drained and renewed. Since
the brake fluid may drip or splash when
pouring it, place plenty of rags around the
master cylinder to protect any surrounding
painted surfaces.
2Before beginning work, purchase the
specified type of brake fluid.
3Remove the cap from the master cylinder
reservoir.
4Using a hand suction pump or similar
device, withdraw the fluid from the master
cylinder reservoir.
5Add new fluid to the master cylinder until it
rises to the base of the filler neck.
6Bleed the brake system as described in
Chapter 9 at all four brakes until new and
uncontaminated fluid flows from the bleed
screw.
7Refill the master cylinder with fluid and
check the operation of the brakes. The pedal
should feel solid when depressed, with no
sponginess.
Warning: Do not drive the car if
you are in any doubt about the
braking system.
1•20Every 30 000 miles or 2 years
27.4 The differential drain plug (arrowed)
is accessible through a hole located in the
middle of the differential support brace
30.3 Push the expansion tank pressure
cap downward and rotate anti-clockwise -
never remove it when the engine is hot!
3261 Jaguar XJ6
Every 60 000 miles (96 000 km)
29 Handbrake shoes check
2
1Remove the rear discs and inspect the
handbrake shoes as described in Chapter 9. If
the shoes are worn or damaged they must be
renewed.Warning: The dust created by
the brake system may contain
asbestos, which is harmful to
your health. Never blow it out
with compressed air and don’t inhale any
of it. An approved filtering mask should be
worn when working on the brakes. Do not,
under any circumstances, use petroleum-
based solvents to clean brake parts. Usebrake system cleaner only! Try to use non-
asbestos replacement parts whenever
possible.
Every 2 years, regardless of mileage

5After the coolant stops flowing out of the
radiator, move the container under the engine
block drain plug. Remove the plug and let the
coolant in the block to drain (see illustration).
6While the coolant is draining from the
engine block, check the condition of the
radiator hoses, heater hoses and clamps
(refer to Section 7 if necessary).
7Replace any damaged clamps or hoses
(see Chapter 3).
Flushing
8Once the system is completely drained,
flush the radiator with fresh water from agarden hose until water runs clear at the drain.
The flushing action of the water will remove
sediments from the radiator but will not
remove more serious rust and scale from the
engine and cooling tube surfaces.
9These deposits can be removed by using
proprietary chemical cleaners. It should be
stressed, however, that these should only
need to be used if the system has been
neglected. Follow the procedure outlined in
their manufacturer’s instructions. If the
radiator is severely corroded, damaged or
leaking, it should be removed (see Chapter 3)
and taken to a radiator repair workshop.10On 1988 and 1989 models remove the
overflow hose from the coolant recovery
reservoir. Drain the reservoir and flush it with
clean water, then reconnect the hose (see
Chapter 3).
Refilling
11Close and tighten the radiator drain. Refit
and tighten the engine block drain plugs.
12Make sure the heater temperature control
is in the maximum heat position.
13Slowly refill the expansion tank with a
mixture of antifreeze and water until the
coolant reaches the base of the filler neck.
14Leave the expansion tank pressure cap
off and run the engine in a well-ventilated area
until the thermostat opens (coolant will begin
flowing through the radiator and the upper
radiator hose will become hot). Race the
engine two or three times under no load.
15Turn the engine off and let it cool. Add
more coolant mixture to bring the level back
up to the base of the filler neck.
16Squeeze the upper radiator hose to expel
air, then add more coolant mixture if
necessary. Refit the expansion tank pressure
cap.
17Start the engine, allow it to reach normal
operating temperature and check for leaks.
Every 2 years 1•21
1
3261 Jaguar XJ6
30.4 The radiator drain fitting (arrowed)
located at the bottom of the radiator30.5 The block drain plug (arrowed) is
located on the right side of the block

Engine block
Deck warpage limit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.076 mm (0.003 inch)
Cylinder bore diameter
Standard
Size group A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90.990 to 91.003 mm (3.5823 to 3.5828 inches)
Size group B . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91.005 to 91.018 mm (3.5829 to 3.5834 inches)
Oversize
0.25 mm (0.010 inch) OS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91.259 to 91.272 mm (3.5929 to 3.5934 inches)
0.50 mm (0.020 inch) OS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91.513 to 91.526 mm (3.6029 to 3.6034 inches)
Pistons and rings
Piston-to-bore clearance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.017 to 0.043 mm (0.0007 to 0.0017 inch)
Piston ring end gap
No.1 (top) compression ring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.40 to 0.66 mm (0.016 to 0.026 inch)
No.2 (middle) compression ring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.40 to 0.66 mm (0.016 to 0.026 inch)
Oil ring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.30 to 0.55 mm (0.012 to 0.022 inch)
Piston ring groove clearance
No. 1 (top) compression ring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.040 to 0.076 mm (0.0016 to 0.0030 inch)
No. 2 (middle) compression ring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.040 to 0.076 mm (0.0016 to 0.0030 inch)
Torque wrench settingsNm lbf ft
Main bearing cap bolts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136 to 142 100 to 105
Connecting rod cap nuts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 to 60 37 to 44
* Note:Refer to Part A for additional torque specifications.
2B•2 Engine removal and overhaul procedures
3261 Jaguar XJ6
1 General information
Included in this portion of Chapter 2 are the
general overhaul procedures for the cylinder
head and internal engine components.
The information ranges from advice
concerning preparation for an overhaul and
the purchase of replacement parts to detailed,
step-by-step procedures covering removal
and refitting of internal engine components
and the inspection of parts.
The following Sections have been written
based on the assumption that the engine has
been removed from the vehicle. For
information concerning in-vehicle engine
repair, as well as removal and refitting of the
external components necessary for the
overhaul, see Part A of this Chapter.
The Specifications included in this Part are
only those necessary for the inspection and
overhaul procedures which follow. Refer to
Part A for additional Specifications.
2 Engine overhaul-
general information
It’s not always easy to determine when, or if,
an engine should be completely overhauled,
as a number of factors must be considered.
High mileage is not necessarily an indication
that an overhaul is needed, while low mileage
doesn’t preclude the need for an overhaul.
Frequency of servicing is probably the most
important consideration. An engine that’s had
regular and frequent oil and filter changes, as
well as other required maintenance, will most
likely give many thousands of miles of reliableservice. Conversely, a neglected engine may
require an overhaul very early in its life.
Excessive oil consumption is an indication
that piston rings, valve seals and/or valve
guides are in need of attention. Make sure that
oil leaks aren’t responsible before deciding
that the rings and/or guides are bad. Perform a
cylinder compression check to determine the
extent of the work required (see Section 4).
Also check the vacuum readings under various
conditions (see Section 3).
Check the oil pressure with a gauge
installed in place of the oil pressure sender
unit (see illustrations)and compare it to this
Chapter’s Specifications. If it’s extremely low,
the bearings and/or oil pump are probably
worn out.
Loss of power, rough running, knocking or
metallic engine noises, excessive valve train
noise and high fuel consumption rates may
also point to the need for an overhaul,
especially if they’re all present at the same
time. If a complete tune-up doesn’t remedy
the situation, major mechanical work is the
only solution.An engine overhaul involves restoring the
internal parts to the specifications of a new
engine. During an overhaul, the piston rings
are replaced and the cylinder walls are
reconditioned (rebored and/or honed). If a
rebore is done by an automotive machine
workshop, new oversize pistons will also be
installed. The main bearings, big-end bearings
and camshaft bearings are generally replaced
with new ones and, if necessary, the
crankshaft may be reground to restore the
journals. Generally, the valves are serviced as
well, since they’re usually in less-than-perfect
condition at this point. While the engine is
being overhauled, other components, such as
the distributor, starter and alternator, can be
rebuilt as well. The end result should be a like
new engine that will give many trouble free
miles. Note:Critical cooling system
components such as the hoses, drivebelts,
thermostat and water pump should be
replaced with new parts when an engine is
overhauled. The radiator should be checked
carefully to ensure that it isn’t clogged or
leaking (see Chapter 3).If you purchase a
2.4a The oil pressure sender unit (arrowed)
is located in the right front corner of the
engine block, near the oil filter2.4b The oil pressure can be checked by
removing the sender unit and refitting a
pressure gauge in its place

rebuilt engine or short block, some rebuilders
will not warranty their engines unless the
radiator has been professionally flushed. Also,
we don’t recommend overhauling the oil
pump - always refit a new one when an engine
is rebuilt.
Before beginning the engine overhaul, read
through the entire procedure to familiarise
yourself with the scope and requirements of
the job. Overhauling an engine isn’t difficult,
but it is time-consuming. Plan on the vehicle
being tied up for a minimum of two weeks,
especially if parts must be taken to an
automotive machine workshop for repair or
reconditioning. Check on availability of parts
and make sure that any necessary special
tools and equipment are obtained in advance.
Most work can be done with typical hand
tools, although a number of precision
measuring tools are required for inspecting
parts to determine if they must be renewed.
Often an automotive machine workshop will
handle the inspection of parts and offer
advice concerning reconditioning and
renewal. Note:Always wait until the engine
has been completely dismantled and all
components, especially the engine block,
have been inspected before deciding what
service and repair operations must be
performed by an automotive machine
workshop. Since the engine block’s condition
will be the major factor to consider when
determining whether to overhaul the original
engine or buy a rebuilt one, never purchase
parts or have machine work done on other
components until the engine block has been
thoroughly inspected. As a general rule, time
is the primary cost of an overhaul, so it
doesn’t pay to refit worn or substandard
parts.
If it turns out that a number of major
components are beyond reconditioning, it
may be cost effective to buy a factory-rebuilt
engine from a Jaguar dealership.
As a final note, to ensure maximum life and
minimum trouble from a rebuilt engine,
everything must be assembled with care in a
spotlessly-clean environment.
3 Vacuum gauge
diagnostic checks
2
A vacuum gauge provides valuable
information about what is going on in the
engine at a low cost. You can check for worn
rings or cylinder walls, leaking cylinder head or
intake manifold gaskets, incorrect carburettor
adjustments, restricted exhaust, stuck or
burned valves, weak valve springs, improper
ignition or valve timing and ignition problems.
Unfortunately, vacuum gauge readings are
easy to misinterpret, so they should be used
with other tests to confirm the diagnosis.
Both the absolute readings and the rate of
needle movement are important for accurate
interpretation. Most gauges measure vacuumin inches of mercury (in-Hg). As vacuum
increases (or atmospheric pressure decreases),
the reading will decrease. Also, for every
1000 foot increase in elevation above sea level;
the gauge readings will decrease about one
inch of mercury.
Connect the vacuum gauge directly to
intake manifold vacuum, not to ported (above
the throttle plate) vacuum (see illustration).
Be sure no hoses are left disconnected during
the test or false readings will result.
Before you begin the test, allow the engine
to warm up completely. Block the wheels and
set the handbrake. With the transmission in
Park, start the engine and allow it to run at
normal idle speed.
Warning: Carefully inspect the
fan blades for cracks or damage
before starting the engine. Keep
your hands and the vacuum
tester clear of the fan and do not stand in
front of the vehicle or in line with the fan
when the engine is running.
Read the vacuum gauge; an average,
healthy engine should normally produce
between 17 and 22 inches of vacuum with a
fairly steady needle.
Refer to the following vacuum gauge
readings and what they indicate about the
engines condition:
1A low steady reading usually indicates a
leaking gasket between the intake manifold
and carburettor or throttle body, a leaky
vacuum hose, late ignition timing or incorrect
camshaft timing. Check ignition timing with a
timing light and eliminate all other possible
causes, utilising the tests provided in this
Chapter before you remove the timing belt
cover to check the timing marks.
2If the reading is three to eight inches below
normal and it fluctuates at that low reading,
suspect an intake manifold gasket leak at an
intake port or a faulty injector.
3If the needle has regular drops of about two
to four inches at a steady rate the valves are
probably leaking. Perform a compression or
leak-down test to confirm this.
4An irregular drop or down-flick of the
needle can be caused by a sticking valve or
an ignition misfire. Perform a compression or
leak-down test and read the spark plugs.5A rapid vibration of about four in-Hg
vibration at idle combined with exhaust
smoke indicates worn valve guides. Perform a
leak-down test to confirm this. If the rapid
vibration occurs with an increase in engine
speed, check for a leaking intake manifold
gasket or cylinder head gasket, weak valve
springs, burned valves or ignition misfire.
6A slight fluctuation, say one inch up and
down, may mean ignition problems. Check all
the usual tune-up items and, if necessary, run
the engine on an ignition analyser.
7If there is a large fluctuation, perform a
compression or leak-down test to look for a
weak or dead cylinder or a blown cylinder
head gasket.
8If the needle moves slowly through a wide
range, check for a clogged PCV system,
incorrect idle fuel mixture, throttle body or
intake manifold gasket leaks.
9Check for a slow return after revving the
engine by quickly snapping the throttle open
until the engine reaches about 2,500 rpm and
let it shut. Normally the reading should drop to
near zero, rise above normal idle reading
(about 5 in.-Hg over) and then return to the
previous idle reading. If the vacuum returns
slowly and doesn’t peak when the throttle is
snapped shut, the rings may be worn. If there
is a long delay, look for a restricted exhaust
system (often the silencer or catalytic
converter). An easy way to check this is to
temporarily disconnect the exhaust ahead of
the suspected part and redo the test.
4 Cylinder compression check
2
1A compression check will tell you what
mechanical condition the upper end (pistons,
rings, valves, cylinder head gasket) of your
engine is in. Specifically, it can tell you if the
compression is down due to leakage caused
by worn piston rings, defective valves and
seats or a blown cylinder head gasket. Note:
The engine must be at normal operating
temperature and the battery must be fully
charged for this check.
2Begin by cleaning the area around the
spark plugs before you remove them
(compressed air should be used, if available,
otherwise a small brush or even a bicycle tyre
pump will work). The idea is to prevent dirt
from getting into the cylinders as the
compression check is being done.
3Remove all of the spark plugs from the
engine (see Chapter 1).
4Block the throttle wide open.
5Detach the coil wire from the centre of the
distributor cap and ground it on the engine
block. Use a jumper wire with alligator clips on
each end to ensure a good earth. Also,
remove the fuel pump relay (see Chapter 4) to
disable the fuel pump during the compression
test.
Engine removal and overhaul procedures 2B•3
2B
3.4 The vacuum gauge is easily attached
to a port on the intake manifold, and can
tell a lot about an engine’s state of tune
3261 Jaguar XJ6