1997 JAGUAR XJ6 compression ratio

1 General information
1This Chapter is designed to help the home
mechanic maintain his/her vehicle for safety,
economy, long life and peak performance.
2The Chapter contains a master
maintenance schedule, followed by Sections
dealing specifically with each task in the
schedule. Visual checks, adjustments,
component renewal and other helpful items
are included. Refer to the accompanying
illustrations of the engine compartment and
the underside of the vehicle for the locations
of the various components.
3Servicing your vehicle in accordance with
the mileage/time maintenance schedule and
the following Sections will provide a planned
maintenance programme, which should result
in a long and reliable service life. This is a
comprehensive plan, so maintaining some
items but not others at the specified service
intervals, will not produce the same results.
4As you service your vehicle, you will
discover that many of the procedures can -
and should - be grouped together, because of
the particular procedure being performed, or
because of the proximity of two otherwise-
unrelated components to one another. For
example, if the vehicle is raised for any
reason, the exhaust can be inspected at the
same time as the suspension and steering
components.
5The first step in this maintenance
programme is to prepare yourself before the
actual work begins. Read through all theSections relevant to the work to be carried out,
then make a list and gather all the parts and
tools required. If a problem is encountered,
seek advice from a parts specialist, or a dealer
service department.
2 Intensive maintenance
1If, from the time the vehicle is new, the
routine maintenance schedule is followed
closely, and frequent checks are made of fluid
levels and high-wear items, as suggested
throughout this manual, the engine will be
kept in relatively good running condition, and
the need for additional work will be minimised.
2It is possible that there will be times when
the engine is running poorly due to the lack of
regular maintenance. This is even more likely
if a used vehicle, which has not received
regular and frequent maintenance checks, is
purchased. In such cases, additional work
may need to be carried out, outside of the
regular maintenance intervals.
3If engine wear is suspected, a compression
test (refer to Chapter 2) will provide valuable
information regarding the overall performance
of the main internal components. Such a test
can be used as a basis to decide on the extent
of the work to be carried out. If, for example, a
compression test indicates serious internal
engine wear, conventional maintenance as
described in this Chapter will not greatly
improve the performance of the engine, and
may prove a waste of time and money, unless
extensive overhaul work is carried out first.4The following series of operations are those
which are most often required to improve the
performance of a generally poor-running
engine:
Primary operations
a) Clean, inspect and test the battery
(Section 6).
b) Check all the engine-related fluids (refer
to “Weekly checks”).
c) Check the condition and tension of the
auxiliary drivebelt (Section 21).
d) Renew the spark plugs (Section 16).
e) Inspect the distributor cap and rotor arm
(Section 19).
f) Check the condition of the air filter, and
renew if necessary (Section 17).
g) Renew the fuel filter (Section 18).
h) Check the condition of all hoses, and
check for fluid leaks (Section 7).
i) Check the exhaust gas emissions (see
Chapter 6).
5If the above operations do not prove fully
effective, carry out the following secondary
operations:
Secondary operations
All items listed under “Primary operations”,
plus the following:
a) Check the charging system (refer to
Chapter 5).
b) Check the ignition system (refer to
Chapter 5).
c) Check the fuel system (refer to Chapter 4).
d) Renew the distributor cap and rotor arm
(Section 19).
e) Renew the ignition HT leads (Section 19).
1•6Maintenance procedures
3261 Jaguar XJ6
Every 7500 miles (12 000 km) or 6 months
3 Engine oil and filter renewal
2
1Frequent oil changes are the best
preventive maintenance the home mechanic
can give the engine, because ageing oil
becomes diluted and contaminated, which
leads to premature engine wear.
2Make sure that you have all the necessary
tools before you begin this procedure (see
illustration). You should also have plenty of
rags or newspapers handy for mopping up
any spills.
3Access to the underside of the vehicle is
greatly improved if the vehicle can be lifted on
a hoist, driven onto ramps or supported by
axle stands.
4If this is your first oil change, get under the
vehicle and familiarise yourself with the
location of the oil drain plug. The engine and
3.2 These tools are required when
changing the engine oil and filter
1 Drain pan - It should be fairly shallow in
depth, but wide in order to prevent spills
2 Rubber gloves - When removing the drain
plug and filter, it is inevitable that you will
get oil on your hands (the gloves will
prevent burns)
3 Breaker bar - Sometimes the oil drain plug
is pretty tight and a long breaker bar is
needed to loosen it
4 Socket – To be used with the breaker bar
or a ratchet (must be the correct size to fit
the drain plug)
5 Filter wrench - This is a metal band-type
wrench, which requires clearance around
the filter to be effective
6 Filter wrench - This type fits on the bottom
of the filter and can be turned with a
ratchet or breaker bar (different size
spanners are available for different types of
filters)

3261 Jaguar XJ6
2A
Chapter 2 Part A
Engine in-car repair procedures
General
Cylinder numbers (front to rear) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2-3-4-5-6
Firing order . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5-3-6-2-4
Displacement:
3.2 litre engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3239 cc
3.6 litre engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3590 cc
4.0 litre engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3980 cc
Bore . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91.0 mm (3.583 inches)
Stroke:
3.2 litre engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83.0 mm (3.268 inches)
3.6 litre engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92.0 mm (3.622 inches)
4.0 litre engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102.0 mm (4.016 inches)
Camshafts and lifters
Journal diameter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26.9370 to 26.9494 mm (1.0605 to 1.0610 inches)
Bearing oil clearance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.037 to 0.063 mm (0.0014 to 0.0024 inch)
Runout limit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.0406 mm (0.0016 inch)
Lobe lift (maximum variation between lobes) . . . . . . . . . . . . . . . . . . . . . 0.0127 mm (0.005 inch)
Valve lifter
Diameter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33.34 to 33.35 mm (1.3126 to 1.3130 inches)
Oil clearance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.020 to 0.050 mm (0.0008 to 0.0020 inch)
Valve clearances . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.30 to 0.36 mm (0.012 to 0.014 inch)
Oil pump
Outer rotor to body clearance, maximum . . . . . . . . . . . . . . . . . . . . . . . 0.2 mm (0.0079 inch)
Outer rotor OD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69.774 to 69.825 mm (2.7470 to 2.7490 inches)
Rotor thickness, inner and outer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27.962 to 27.975 mm (1.1008 to 1.1013 inches)
Clearance over rotors, maximum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.1 mm (0.0039 inch) Auxiliary shaft - renewal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Camshafts and lifters - removal, inspection and refitting . . . . . . . . . 10
CHECK ENGINE light . . . . . . . . . . . . . . . . . . . . . . . . . . . See Chapter 6
Crankshaft front oil seal - renewal . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Crankshaft rear oil seal - renewal . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Cylinder compression check . . . . . . . . . . . . . . . . . . . . See Chapter 2B
Cylinder head - removal and refitting . . . . . . . . . . . . . . . . . . . . . . . . 11
Drivebelt check, adjustment and renewal . . . . . . . . . . . See Chapter 1
Driveplate - removal and refitting . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Engine mounts - check and renewal . . . . . . . . . . . . . . . . . . . . . . . . . 16
Engine oil and filter change . . . . . . . . . . . . . . . . . . . . . . See Chapter 1
Engine overhaul - general information . . . . . . . . . . . . . See Chapter 2B
Engine - removal and refitting . . . . . . . . . . . . . . . . . . . See Chapter 2BExhaust manifolds - removal and refitting . . . . . . . . . . . . . . . . . . . . . 6
General information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Intake manifold - removal and refitting . . . . . . . . . . . . . . . . . . . . . . . 5
Sump - removal and refitting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Oil pump - removal, inspection and refitting . . . . . . . . . . . . . . . . . . . 13
Repair operations possible with the engine in the vehicle . . . . . . . . 2
Spark plug renewal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . See Chapter 1
Timing chains and sprockets - removal, inspection and refitting . . . 8
Top Dead Centre (TDC) for number one piston - locating . . . . . . . . . 3
Valve cover - removal and refitting . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Valves - servicing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . See Chapter 2B
Water pump - removal and refitting . . . . . . . . . . . . . . . . See Chapter 3
2A•1
Specifications Contents
Easy,suitable for
novice with little
experienceFairly easy,suitable
for beginner with
some experienceFairly difficult,
suitable for competent
DIY mechanic
Difficult,suitable for
experienced DIY
mechanicVery difficult,
suitable for expert DIY
or professional
Degrees of difficulty
54321

Torque wrench settings*Nm lbf ft
Camshaft bearing cap bolts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 to 27 16 to 20
Camshaft sprocket bolts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 to 27 16 to 20
Crankshaft damper-to-crankshaft bolt
3.2 and 3.6 litre . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 204 151
4.0 litre . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 180 to 220 133 to 162
Crankshaft pulley to damper bolts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 to 27 16 to 20
Crankshaft rear oil seal retainer bolts . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 to 27 16 to 20
Crankshaft sensor bolts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 to 27 16 to 20
Cylinder head bolts
Step 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60 44
Step 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Tighten an additional 90° (1/4 turn)
Driveplate bolts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123 to 149 91 to 110
Engine mounts
To engine block . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 to 66 36 to 39
To chassis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 to 24 16 to 18
Exhaust manifold heat shield fasteners . . . . . . . . . . . . . . . . . . . . . . . . . 23 to 27 16 to 20
Exhaust manifold nuts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 to 27 16 to 20
Intake manifold nuts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 to 27 16 to 20
Oil pump bolts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 to 27 16 to 20
Sump bolts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 to 27 16 to 20
Sump bolts, adapter to pan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 to 54 36 to 40
Timing chain cover . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 to 27 16 to 20
Valve cover screws . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 to 12 7 to 9
*Note:Refer to Part B for additional specifications
2A•2 Engine in-car repair procedures
3261 Jaguar XJ6
1 General information
This Part of Chapter 2 is devoted to in-car
repair procedures for the in-line six-cylinder
engines. All information concerning engine
removal and refitting and engine block and
cylinder head overhaul can be found in Part B
of this Chapter.
The following repair procedures are based
on the assumption that the engine is installed
in the car. If the engine has been removed
from the car and mounted on a stand, many of
the steps outlined in this Part of Chapter 2 will
not apply. We have photographed some in-
car engine procedures with the engine on a
stand for photographic purposes.
The Specifications included in this Part of
Chapter 2 apply only to the procedures
contained in this Part. Part B of Chapter 2
includes the Specifications necessary for
cylinder head and engine block rebuilding.
2 Repair operations possible
with the engine in the car
Many repair operations can be
accomplished without removing the engine
from the car.
Clean the engine compartment and the
exterior of the engine with some type of
degreaser before any work is done. It will
make the job easier and help keep dirt out of
the internal areas of the engine.
Depending on the components involved, itmay be helpful to remove the bonnet to
improve access to the engine as repairs are
performed (refer to Chapter 11 if necessary).
Cover the wings to prevent damage to the
paint. Special pads are available, but an old
bedspread or blanket will also work.
If vacuum, exhaust, oil or coolant leaks
develop, indicating a need for gasket or seal
renewal, the repairs can generally be made
with the engine in the car. The intake and
exhaust manifold gaskets, crankshaft oil seals
and cylinder head gasket are all accessible
with the engine in place (although rear oil seal
renewal involves removal of the transmission).
The sump is difficult for a home mechanic to
replace without a hoist and other specialised
equipment, since the front suspension,
steering and crossmember must be lowered
to allow enough clearance for sump removal.
If such equipment is not available, the
alternative would be to remove the engine for
renewal of the sump or oil pump. Note:We
assume that the home mechanic does not
have access to the specialised equipment,
and have photographed our subject engine
out of the car for some procedures.
Exterior engine components, such as the
intake and exhaust manifolds, the water
pump, the starter motor, the alternator, the
distributor and the fuel system components
can be removed for repair with the engine in
place.
Since the cylinder head can be removed
with the engine in-car, camshaft and valve
component servicing can also be
accomplished. Renewal of the timing chains
and sprockets is also possible with the engine
in-car.
3 Top Dead Centre (TDC) for
number one piston- locating
1
Note:The following procedure is based on the
assumption that the distributor is correctly
installed. If you are trying to locate TDC to refit
the distributor correctly, piston position must
be determined by feeling for compression at
the number one spark plug hole, then aligning
the ignition timing marks (see paragraph 8).
1Top Dead Centre (TDC) is the highest point
in the cylinder that each piston reaches as it
travels up the cylinder bore. Each piston
reaches TDC on the compression stroke and
again on the exhaust stroke, but TDC
generally refers to piston position on the
compression stroke.
2Positioning the piston(s) at TDC is an
essential part of many procedures such as
camshaft and timing chain/sprocket removal
and distributor removal.
3Before beginning this procedure, be sure to
place the transmission in Neutral and apply
the handbrake or block the rear wheels. Also,
disable the ignition system by detaching the
coil wire from the centre terminal of the
distributor cap and grounding it on the engine
block with a jumper wire. Remove the spark
plugs (see Chapter 1).
4In order to bring any piston to TDC, the
crankshaft must be turned using one of the
methods outlined below. When looking at the
timing chain end of the engine, normal
crankshaft rotation is clockwise.
a) The preferred method is to turn the
crankshaft with a socket and ratchet

attached to the bolt threaded into the
front of the crankshaft. Apply pressure on
the bolt in a clockwise direction only.
Never turn the bolt anti-clockwise.
b) A remote starter switch, which may save
some time, can also be used. Follow the
instructions included with the switch.
Once the piston is close to TDC, use a
socket and ratchet as described in the
previous paragraph.
c) If an assistant is available to turn the
ignition switch to the Start position in
short bursts, you can get the piston close
to TDC without a remote starter switch.
Make sure your assistant is out of the car,
away from the ignition switch, then use a
socket and ratchet as described in
Paragraph a) to complete the procedure.
5Note the position of the terminal for the
number one spark plug lead on the distributor
cap. If the terminal isn’t marked, follow the
plug lead from the number one cylinder spark
plug to the cap.
6Use a felt-tip pen or chalk to make a mark
on the distributor body directly under the
number one terminal (see Chapter 5).
7Detach the cap from the distributor and set
it aside (see Chapter 1 if necessary).
8Turn the crankshaft until the small triangle
cast into the front edge of the crankshaft
sensor ring is aligned with the bottom edge of
the timing pointer located at the front of the
engine(see illustration).
9Look at the distributor rotor - it should be
pointing directly at the mark you made on the
distributor body. If so, you are at TDC for
number 1 cylinder.
10If the rotor is 180° off, the number one
piston is at TDC on the exhaust stroke.
11To get the piston to TDC on the
compression stroke, turn the crankshaft one
complete revolution (360°) clockwise. The
rotor should now be pointing at the mark
on the distributor. When the rotor is pointing
at the number one spark plug lead terminal in
the distributor cap and the ignition timing
marks are aligned, the number one piston is atTDC on the compression stroke. Note:If it’s
impossible to align the ignition timing marks
when the rotor is pointing at the mark on the
distributor body, the timing chain may have
jumped the teeth on the pulleys or may have
been installed incorrectly.
12After the number one piston has been
positioned at TDC on the compression stroke,
TDC for any of the remaining cylinders can be
located by turning the crankshaft and
following the firing order. Mark the remaining
spark plug lead terminal locations on the
distributor body just like you did for the
number one terminal, then number the marks
to correspond with the cylinder numbers. As
you turn the crankshaft, the rotor will also
turn. When it’s pointing directly at one of the
marks on the distributor, the piston for that
particular cylinder is at TDC on the
compression stroke.
4 Valve cover-
removal and refitting
1
Removal
1Disconnect the battery negative cable.
Caution: If the stereo in your vehicle is
equipped with an anti-theft system, makesure you have the correct activation code
before disconnecting the battery.
2Detach the PCV hose from the valve cover
(see illustration).
3Remove the spark plug leads from the
spark plugs, handling them by the boots and
not pulling on the wires.
4Remove the valve cover mounting screws,
then detach the valve cover and gasket from
the cylinder head. If the valve cover is stuck
to the cylinder head, bump the end with a
wood block and a hammer to jar it loose. If
that doesn’t work, try to slip a flexible putty
knife between the cylinder head and valve
cover to break the seal.
Caution: Don’t pry at the valve cover-to-
cylinder head joint or damage to the
sealing surfaces may occur, leading to oil
leaks after the valve cover is reinstalled.
Refitting
5The mating surfaces of the cylinder head
and valve cover must be clean when the valve
cover is installed. If there’s residue or oil on
the mating surfaces when the valve cover is
installed, oil leaks may develop.
6Apply RTV sealant around the two half-
circle rubber plugs at the rear of the cylinder
head (see illustration).
7Using a new gasket and spark plug tube
seals, refit the valve cover (see illustration).
Engine in-car repair procedures 2A•3
2A
4.6 Apply RTV sealant to the half-circle
plugs and insert them into the cylinder
head before refitting the valve cover4.7 Press the valve cover gasket into the
groove around the valve cover and fit a
new set of spark plug tube seals (arrowed)
3261 Jaguar XJ6 3.8 Align the mark on the crankshaft sensor ring (arrowed) with
the bottom edge of the pointer on the front cover
4.2 Disconnect the PCV hose (arrowed) from the valve cover, then
pull the spark plug leads out by their boots, not the leads

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

6Refit the compression gauge in the spark
plug hole (see illustration).
7Crank the engine over at least seven
compression strokes and watch the gauge.
The compression should build up quickly in a
healthy engine. Low compression on the first
stroke, followed by gradually increasing
pressure on successive strokes, indicates
worn piston rings. A low compression reading
on the first stroke, which doesn’t build up
during successive strokes, indicates leaking
valves or a blown cylinder head gasket (a
cracked cylinder head could also be the
cause). Deposits on the undersides of the
valve heads can also cause low compression.
Record the highest gauge reading obtained.
8Repeat the procedure for the remaining
cylinders and compare the results to this
Chapter’s Specifications.
9Add some engine oil (about three squirts
from a plunger-type oil can) to each cylinder,
through the spark plug hole, and repeat the
test.
10If the compression increases after the oil
is added, the piston rings are definitely worn.
If the compression doesn’t increase
significantly, the leakage is occurring at the
valves or cylinder head gasket. Leakage past
the valves may be caused by burned valve
seats and/or faces or warped, cracked or bent
valves.
11If two adjacent cylinders have equally low
compression, there’s a strong possibility that
the cylinder head gasket between them is
blown. The appearance of coolant in the
combustion chambers or the crankcase
would verify this condition.
12If one cylinder is 20 percent lower than the
others, and the engine has a slightly rough
idle, a worn exhaust lobe on the camshaft
could be the cause.
13If the compression is unusually high, the
combustion chambers are probably coated
with carbon deposits. If that’s the case, the
cylinder head(s) should be removed and
decarbonised.
14If compression is way down or varies
greatly between cylinders, it would be a goodidea to have a leak-down test performed by
an automotive repair workshop. This test will
pinpoint exactly where the leakage is
occurring and how severe it is.
5 Engine removal-
methods and precautions
If you’ve decided that an engine must be
removed for overhaul or major repair work,
several preliminary steps should be taken.
Locating a suitable place to work is
extremely important. Adequate work space,
along with storage space for the vehicle, will
be needed. If a workshop or garage isn’t
available, at the very least a flat, level, clean
work surface made of concrete or asphalt is
required.
Cleaning the engine compartment and
engine before beginning the removal
procedure will help keep tools clean and
organised.
An engine hoist or A-frame will also be
necessary. Make sure the equipment is rated
in excess of the combined weight of the
engine and transmission. Safety is of primary
importance, considering the potential hazards
involved in lifting the engine out of the vehicle.
If the engine is being removed by a novice,
a helper should be available. Advice and aid
from someone more experienced would also
be helpful. There are many instances when
one person cannot simultaneously perform all
of the operations required when lifting the
engine out of the vehicle.
Plan the operation ahead of time. Arrange
for or obtain all of the tools and equipment
you’ll need prior to beginning the job. Some of
the equipment necessary to perform engine
removal and refitting safely and with relative
ease are (in addition to an engine hoist) a
heavy duty trolley jack, complete sets of
spanners and sockets as described in the
front of this manual, wooden blocks and
plenty of rags and cleaning solvent for
mopping up spilled oil, coolant and petrol. If
the hoist must be rented, make sure that you
arrange for it in advance and perform all of the
operations possible without it beforehand.
This will save you money and time.
Plan for the vehicle to be out of use for
quite a while. A machine workshop will be
required to perform some of the work which
the do-it-yourselfer can’t accomplish without
special equipment. These shops often have a
busy schedule, so it would be a good idea to
consult them before removing the engine in
order to accurately estimate the amount of
time required to rebuild or repair components
that may need work.
Always be extremely careful when removing
and refitting the engine. Serious injury can
result from careless actions. Plan ahead, take
your time and a job of this nature, although
major, can be accomplished successfully.
6 Engine- removal and refitting
3
Note:Read through the entire Section before
beginning this procedure. It is recommended
to remove the engine and transmission from
the top as a unit, then separate the engine
from the transmission on the workshop floor. If
the transmission is not being serviced, it is
possible to leave the transmission in the
vehicle and remove the engine from the top by
itself, by removing the crankshaft damper and
tilting up the front end of the engine for
clearance,but access to the upper
bellhousing bolts is only practical when the
rear transmission mount and driveshaft have
been removed and the transmission is angled
down with a trolley jack.
Removal
1Relieve the fuel system pressure (see
Chapter 4).
2Disconnect the battery negative cable.
Caution: If the stereo in your vehicle is
equipped with an anti-theft system, make
sure you have the correct activation code
before disconnecting the battery.
3Place protective covers on the wings and
cowl and remove the bonnet (see Chapter 11).
4Remove the battery and battery tray.
5Remove the air cleaner assembly (see
Chapter 4).
6Raise the vehicle and support it securely on
axle stands. Drain the cooling system and
engine oil and remove the drivebelts (see
Chapter 1).
7Clearly label, then disconnect all vacuum
lines, coolant and emissions hoses, wiring
harness connectors and earth straps.
Masking tape and/or a touch up paint
applicator work well for marking items (see
illustration). Take instant photos or sketch
the locations of components and brackets.
8Remove the cooling fan(s) and radiator (see
Chapter 3).
9Disconnect the heater hoses.
10Release the residual fuel pressure in the
tank by removing the petrol cap, then detach
the fuel lines connecting the engine to the
chassis (see Chapter 4). Plug or cap all open
fittings.
2B•4 Engine removal and overhaul procedures
4.6 A compression gauge with a threaded
fitting for the spark plug hole is preferred
over the type that requires hand pressure
to maintain the seal - be sure to block
open the throttle valve as far as possible
during the compression check!
6.7 Label both ends of each wire and hose
before disconnecting it
3261 Jaguar XJ6

the upper and lower side rails can be turned
smoothly in the ring groove.
11The number two (middle) ring is installed
next. It’s usually stamped with a mark which
must face up, toward the top of the piston.
Note:Always follow the instructions on the
ring package or box - different manufacturers
may require different approaches. Do not mix
up the top and middle rings, as they have
different cross sections.
12Use a piston ring refitting tool and make
sure the ring’s identification mark is facing the
top of the piston, then slip the ring into the
middle groove on the piston (see illustration).
Don’t expand the ring any more than
necessary to slide it over the piston.
13Refit the number one (top) ring in the
same manner. Make sure the mark is facing
up. Be careful not to confuse the number one
and number two rings.
14Repeat the procedure for the remaining
pistons and rings.
23 Crankshaft- refitting and
main bearing oil clearance
check
3
1Crankshaft refitting is the first major step in
engine reassembly. It’s assumed at this point
that the engine block and crankshaft have
been cleaned, inspected and repaired or
reconditioned.
2Position the engine with the bottom facing
up.
3Remove the main bearing cap bolts and lift
out the caps. Lay the caps out in the proper
order.
4If they’re still in place, remove the old
bearing inserts from the engine block and the
main bearing caps. Wipe the main bearing
surfaces of the engine block and caps with a
clean, lint free cloth. They must be kept
spotlessly clean!
Main bearing
oil clearance check
5Clean the back sides of the new main
bearing inserts and lay the bearing half with
the oil groove in each main bearing saddle inthe engine block. Lay the other bearing half
from each bearing set in the corresponding
main bearing cap. Make sure the tab on each
bearing insert fits into the recess in the engine
block or cap. Also, the oil holes in the block
must line up with the oil holes in the bearing
insert.
Caution: Do not hammer the bearings into
place and don’t nick or gouge the bearing
faces. No lubrication should be used at this
time.
6The thrust bearings (washers) must be
installed in the number four main bearing cap
and saddle.
7Clean the faces of the bearings in the
engine block and the crankshaft main bearing
journals with a clean, lint free cloth. Check or
clean the oil holes in the crankshaft, as any
dirt here can go only one way - straight
through the new bearings.
8Once you’re certain the crankshaft is clean,
carefully lay it in position in the main bearings.
9Before the crankshaft can be permanently
installed, the main bearing oil clearance must
be checked.
10Trim several pieces of the appropriate size
Plastigauge (they must be slightly shorter than
the width of the main bearings) and place one
piece on each crankshaft main bearing
journal, parallel with the journal axis (see
illustration).
11Clean the faces of the bearings in the
caps and refit the caps in their respective
positions (don’t mix them up) with the arrows
pointing toward the front of the engine. Don’t
disturb the Plastigauge. Apply a light coat of
oil to the bolt threads and the undersides of
the bolt heads, then refit them. Note:Use the
old bolts for this step (save the new bolts for
final refitting).
12Tighten the main bearing cap bolts, in
three steps, to the torque listed in this
Chapter’s Specifications. Don’t rotate the
crankshaft at any time during this operation!
13Remove the bolts and carefully lift off the
main bearing caps or cap assembly. Keep
them in order. Don’t disturb the Plastigauge or
rotate the crankshaft. If any of the main
bearing caps are difficult to remove, tap them
gently from side-to-side with a soft-face
hammer to loosen them.14Compare the width of the crushed
Plastigauge on each journal to the scale printed
on the Plastigauge envelope to obtain the main
bearing oil clearance (see illustration). Check
the Specifications to make sure it’s correct.
15If the clearance is not as specified, the
bearing inserts may be the wrong size (which
means different ones will be required - see
Section 20). Before deciding that different
inserts are needed, make sure that no dirt or
oil was between the bearing inserts and the
caps or engine block when the clearance was
measured. If the Plastigauge is noticeably
wider at one end than the other, the journal
may be tapered (see Section 19).
16Carefully scrape all traces of the
Plastigauge material off the main bearing
journals and/or the bearing faces. Don’t nick
or scratch the bearing faces.
Final crankshaft refitting
17Carefully lift the crankshaft out of the
engine. Clean the bearing faces in the engine
block, then apply a thin, uniform layer of clean
moly-base grease or engine assembly lube to
each of the bearing surfaces. Coat the thrust
washers as well.
18Lubricate the crankshaft surfaces that
contact the oil seals with moly-base grease,
engine assembly lube or clean engine oil.
19Make sure the crankshaft journals are
clean, then lay the crankshaft back in place in
the engine block. Clean the faces of the
bearings in the main bearing caps, then apply
lubricant to them. Refit the main bearing caps
in their respective positions with the arrows
pointing toward the front of the engine. Note:
Be sure to refit the thrust washers (lubricated)
with the number 4 main journal.The upper
(block side) thrust washers can be rotated into
position around the crankshaft with the
crankshaft installed in the engine block, with
the thrust washer grooves facing OUT. The
lower thrust washers should be placed on the
main bearing caps with their grooves OUT.
20For the final assembly, use only new
bolts, for both the main bearings and the
2B•16 Engine removal and overhaul procedures
23.10 Lay the Plastigauge strips on the
main bearing journals, parallel to the
crankshaft centreline
23.14 Compare the width of the crushed
Plastigauge to the scale on the envelope to
determine the main bearing oil clearance
(always take the measurement at the
widest point of the Plastigauge). Be sure to
use the correct scale - imperial and metric
scales are included
3261 Jaguar XJ6
22.12 Refit the compression rings with a
ring expander - the mark must face up