1997 JAGUAR XJ6 width

compressor belt first because of the way they
are arranged on the crankshaft pulley.
Because of this and because belts tend to
wear out more or less together, it is a good
idea to replace both belts at the same time.
Mark each belt and its appropriate pulley
groove so the new belts can be installed in
their proper positions.
10Take the old belts to the parts store in
order to make a direct comparison for length,
width and design.
11After replacing a ribbed drivebelt, make
sure that it fits properly in the ribbed grooves
in the pulleys (see illustration). It is essential
that the belt be properly centred.
12Adjust the belt(s) in accordance with the
procedure outlined above.
22 Front wheel bearing check
and adjustment
3
Check and repack
1In most cases the front wheel bearings will
not need servicing until the brake pads are
changed. However, the bearings should be
checked whenever the front of the vehicle is
raised for any reason. Several items, including
a torque wrench and special grease, are
required for this procedure (see illustration).2With the vehicle securely supported on axle
stands, spin each wheel and check for noise,
rolling resistance and freeplay.
3Grasp the top of each tyre with one hand
and the bottom with the other. Move the
wheel in-and-out on the spindle. If there’s any
noticeable movement, the bearings should be
checked and then repacked with grease or
renewed if necessary.
4Remove the wheel.
5Remove the brake caliper (see Chapter 9)
and hang it out of the way on a piece of wire.
A wood block of the appropriate width can be
slid between the brake pads to keep them
separated, if necessary. Also remove the
brake disc.
6Pry the dust cap out of the hub using a
screwdriver or a hammer and chisel (see
illustration).
7Straighten the bent ends of the cotter pin,
then pull the cotter pin out of the nut lock (see
illustration).Discard the cotter pin and use a
new one during reassembly.
8Remove the locknut, nut and washer from
the end of the spindle.
9Pull the hub out slightly, then push it back
into its original position. This should force theouter bearing off the spindle enough so it can
be removed (see illustration).
10Pull the hub off the spindle. Note:
Sometimes the inner wheel bearing and
grease seal remain attached to the spindle.
Grasp the back of the seal with both hands
and pull forward to remove them.
11If the grease seal is not already detached
from the hub, use a screwdriver to pry the seal
out of the rear of the hub. As this is done, note
how the seal is installed.
12If the inner wheel bearing is not already
detached from the hub, remove it at this time.
13Use solvent to remove all traces of the old
grease from the bearings, hub and spindle. A
small brush may prove helpful; however make
sure no bristles from the brush embed
themselves inside the bearing rollers. Allow
the parts to air dry.
14Carefully inspect the bearings for cracks,
heat discoloration, worn rollers, etc. Check
the bearing races inside the hub for wear and
damage. If the bearing races are defective,
the hubs should be taken to a machine
workshop with the facilities to remove the old
races and press new ones in. Note that the
bearings and races come as matched sets
Every 15 000 miles or 12 months 1•17
1
22.1 Tools and materials needed for front
wheel bearing maintenance
1 Hammer
2 Grease - High-temperature grease that is
formulated specially for front wheel
bearings should be used
3 Wood block - If you have a scrap piece
of 2x4, it can be used to drive the new
seal into the hub
4 Needle-nose pliers - Used to straighten
and remove the cotter pin in the spindle
5 Torque wrench - This is very important in
this procedure; if the bearing is too tight,
the wheel won’t turn freely - if it’s too
loose, the wheel will “wobble” on the
spindle. Either way, it could mean
extensive damage
6 Screwdriver - Used to remove the seal
from the hub (a long screwdriver is
preferred)
7 Socket/breaker bar - Needed to loosen the
nut on the spindle if it’s extremely tight
8 Brush - Together with some clean
solvent, this will be used to remove old
grease from the hub and spindle
22.6 Dislodge the dust cap by working
around the outer circumference with a
hammer and chisel
22.7 Remove the cotter pin and discard it -
use a new one when the hub is reinstalled22.9 Pull the hub assembly forward
slightly - then push it back into position to
dislodge the outer wheel bearing
3261 Jaguar XJ6 21.11 When refitting ribbed (serpentine)
drivebelts, make sure the belt is centred
between the pulley edges (arrowed) - it
must not overlap either edge of the pulley

15Check the valve stem-to-guide clearance
with a small hole gauge and micrometer, or a
small dial bore gauge (see illustration). Also,
check the valve stem deflection with a dial
indicator attached securely to the cylinder
head. The valve must be in the guide and
approximately 1/16-inch off the seat. The total
valve stem movement indicated by the gauge
needle must be noted, then divided by two to
obtain the actual clearance value. If it exceeds
the stem-to-guide clearance limit found in this
Chapter’s Specifications, the valve guides
should be renewed. After this is done, if
there’s still some doubt regarding the
condition of the valve guides they should be
checked by an automotive machine workshop
(the cost should be minimal).
Valves
16Carefully inspect each valve face for
uneven wear, deformation, cracks, pits and
burned areas. Check the valve stem for
scuffing and galling and the neck for cracks.
Rotate the valve and check for any obvious
indication that it’s bent. Look for pits and
excessive wear on the end of the stem. The
presence of any of these conditions indicates
the need for valve service by an automotive
machine workshop.
17Measure the margin width on each valve
(see illustration). Any valve with a margin
narrower than 1/32-inch will have to be
replaced with a new valve.
Valve components
18Check each valve spring for wear (on the
ends) and pits. Measure the free length and
compare it to this Chapter’s Specifications
(see illustration). Any springs that are shorter
than specified have sagged and should not be
re-used. The tension of all springs should be
pressure checked with a special fixture before
deciding that they’re suitable for use in a
rebuilt engine (take the springs to an
automotive machine workshop for this check).
Note:If any valve springs are found broken on
1988 or 1989 engines, all springs should be
replaced with the improved springs used in
1990 (after VIN 9EPCLA120245) and later
engines. They are identified with a white
stripe. If your engine has springs with white-
stripes, they have already been replaced, and
only broken ones need be replaced.
19Stand each spring on a flat surface and
check it for squareness (see illustration). If
any of the springs are distorted or sagged,
renew all of the springs.
20Check the spring retainers and keepers
for obvious wear and cracks. Any
questionable parts should be renewed, as
extensive damage will occur if they fail during
engine operation.
21If the inspection process indicates that the
valve components are in generally poor
condition and worn beyond the limits specified,
which is usually the case in an engine that’s
being overhauled, reassemble the valves in the
cylinder head and refer to Section 11 for valve
servicing recommendations.
11 Valves- servicing
5
1Because of the complex nature of the job
and the special tools and equipment needed,
servicing of the valves, the valve seats and the
valve guides, commonly known as a valve job,
should be done by a professional.
2The home mechanic can remove and
dismantle the cylinder head(s), do the initial
cleaning and inspection, then reassemble and
deliver them to a dealer service department or
an automotive machine workshop for the
actual service work. Doing the inspection will
enable you to see what condition the cylinder
head(s) and valvetrain components are in and
will ensure that you know what work and new
parts are required when dealing with an
automotive machine workshop.
3The dealer service department, or
automotive machine workshop, will remove
the valves and springs, will recondition or
renew the valves and valve seats, recondition
the valve guides, check and renew the valve
springs, spring retainers and keepers (as
necessary), replace the valve seals with new
ones, reassemble the valve components and
make sure the installed spring height is
correct. The cylinder head gasket surface will
also be resurfaced if it’s warped.
4After the valve job has been performed by a
professional, the cylinder head(s) will be in like
new condition. When the cylinder heads are
returned, be sure to clean them again before
refitting on the engine to remove any metal
particles and abrasive grit that may still be
present from the valve service or cylinder
head resurfacing operations. Use compressed
air, if available, to blow out all the oil holes and
passages.
12 Cylinder head- reassembly
2
1Regardless of whether or not the cylinder
head was sent to an automotive machine
workshop for valve servicing, make sure it’s
clean before beginning reassembly. Renew
the cylinder head rear plate gasket any time
that the engine is overhauled or the cylinder
head is reconditioned (see Part A of this
Chapter for renewal procedure).
2If the cylinder head was sent out for valve
servicing, the valves and related components
will already be in place. Begin the reassembly
procedure with paragraph 8.
3Refit new seals on each of the valve guides.
Gently push each valve seal into place until
it’s seated on the guide.
Caution: Don’t hammer on the valve seals
once they’re seated or you may damage
them. Don’t twist or cock the seals during
refitting or they won’t seat properly on the
valve stems.
2B•8 Engine removal and overhaul procedures
10.15 Use a small dial bore gauge to
determine the inside diameter of the valve
guides - subtract the valve stem diameter
to determine the stem-to-guide clearance10.17 The margin width on each valve
must be as specified (if no margin exists,
the valve cannot be re-used)
10.18 Measure the free length of each
valve spring with a dial or vernier caliper10.19 Check each valve spring for
squareness
3261 Jaguar XJ6

21 Engine overhaul-
reassembly sequence
1Before beginning engine reassembly, make
sure you have all the necessary new parts,
gaskets and seals as well as the following
items on hand:
Common hand tools
A 1/2-inch drive torque wrench
Piston ring refitting tool
Piston ring compressor
Short lengths of rubber or plastic hose to
fit over connecting rod bolts
Plastigauge
Feeler gauges
A fine-tooth file
New engine oil
Engine assembly lube or moly-base
grease
Gasket sealer
Thread locking compound
Special Jaguar tools:
Engine lifting brackets (18G 1465)
Timing damper simulator (18E 1436)
Camshaft TDC tool (18G 1433)
2In order to save time and avoid problems,
engine reassembly must be done in the
following general order:
Piston rings (Part B)
Crankshaft and main bearings (Part B)
Piston/connecting rod assemblies (Part B)
Rear main (crankshaft) oil seal (Part B)
Auxiliary shaft (Part A)
Timing chains and sprockets (Part A)
Oil pump (Part A)
Timing chain cover (Part A)
Cylinder head and lifters (Part A)
Camshafts (Part A)
Oil pick-up (Part A)
Sump (Part A)
Intake and exhaust manifolds (Part A)
Valve cover (Part A)
Flywheel/driveplate (Part A)
22 Piston rings- refitting
3
1Before refitting the new piston rings, the ring
end gaps must be checked. It’s assumed that
the piston ring groove clearance has been
checked and verified correct (see Section 18).
2Lay out the piston/connecting rod
assemblies and the new ring sets so the ring
sets will be matched with the same piston and
cylinder during the end gap measurement and
engine assembly.
3Insert the top (number one) ring into the first
cylinder and square it up with the cylinder
walls by pushing it in with the top of the piston
(see illustration). The ring should be near the
bottom of the cylinder, at the lower limit of
ring travel.
4To measure the end gap, slip feeler gauges
between the ends of the ring until a gauge
equal to the gap width is found (see
illustration). The feeler gauge should slide
between the ring ends with a slight amount of
drag. Compare the measurement to that
found in this Chapter’s Specifications. If the
gap is larger or smaller than specified,
double-check to make sure you have the
correct rings before proceeding.
5If the gap is too small, it must be enlarged
or the ring ends may come in contact with
each other during engine operation, which
can cause serious damage to the engine. The
end gap can be increased by filing the ring
ends very carefully with a fine file. Mount thefile in a vice equipped with soft jaws, slip the
ring over the file with the ends contacting the
file face and slowly move the ring to remove
material from the ends(see illustration).
Caution: When performing this operation,
file only from the outside in, and after the
correct gap is achieved, deburr the filed
ends of the rings with a fine whetstone.
6Excess end gap isn’t critical unless it’s
greater than Specifications. Again, double-
check to make sure you have the correct rings
for your engine.
7Repeat the procedure for each ring that will
be installed in the first cylinder and for each
ring in the remaining cylinders. Remember to
keep rings, pistons and cylinders matched.
8Once the ring end gaps have been
checked/corrected, the rings can be installed
on the pistons.
9The oil control ring (lowest one on the
piston) is usually installed first. It’s composed
of three separate components. Slip the
spacer/expander into the groove (see
illustration). If an anti-rotation tang is used,
make sure it’s inserted into the drilled hole in
the ring groove. Next, refit the lower side rail.
Don’t use a piston ring refitting tool on the oil
ring side rails, as they may be damaged.
Instead, place one end of the side rail into the
groove between the spacer/expander and the
ring land, hold it firmly in place and slide a
finger around the piston while pushing the rail
into the groove (see illustrations). Next, refit
the upper side rail in the same manner.
10After the three oil ring components have
been installed, check to make sure that both
Engine removal and overhaul procedures 2B•15
2B
22.3 When checking piston ring end gap,
the ring must be square in the cylinder
bore (this is done by pushing the ring down
with the top of a piston as shown)22.4 With the ring square in the cylinder,
measure the end gap with a feeler gauge22.5 If the end gap is too small, clamp a
file in a vice and file the ring ends (from the
outside in only) to enlarge the gap slightly
22.9a Refit the spacer/expander in the oil
control ring groove22.9b DO NOT use a piston ring refitting
tool when refitting the oil ring side rails
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

connecting rods. Apply a light coat of oil to
the bolt threads and the under sides of the
bolt heads, then refit them. Tighten all main
bearing cap bolts to the torque listed in this
Chapter’s Specifications, starting in the centre
and working out to the ends.
21Rotate the crankshaft a number of times
by hand to check for any obvious binding.
22Check the crankshaft endplay with a
feeler gauge or a dial indicator as described in
Section 14. The endplay should be correct if
the crankshaft thrust faces aren’t worn or
damaged and new thrust washers have been
installed. Note:If the end-play is too great,
even with the new thrust bearings, oversized
thrust bearings are available. There are two
sizes, 0.005-inch and 0.010-inch oversize.
23Refit a new rear main oil seal, then bolt the
retainer to the engine block (see Section 24).
24 Rear main oil seal refitting
2
1The crankshaft must be installed first and
the main bearing caps bolted in place, then
the new seal should be installed in the retainer
and the retainer bolted to the engine block.
2Check the seal contact surface on the
crankshaft very carefully for scratches and
nicks that could damage the new seal lip and
cause oil leaks. If the crankshaft is damaged,
the only alternative is a new or different
crankshaft.
3Refer to Part A of this Chapter for refitting
of the new rear seal, using the plastic
alignment tool supplied with the engine
overhaul gasket set.
25 Pistons/connecting rods-
refitting and big-end bearing
oil clearance check
3
1Before refitting the piston/connecting rod
assemblies, the cylinder walls must be
perfectly clean, the top edge of each cylinder
must be chamfered, and the crankshaft must
be in place.
2Remove the cap from the end of the
number one connecting rod (refer to the
marks made during removal). Remove the
original bearing inserts and wipe the bearing
surfaces of the connecting rod and cap with a
clean, lint-free cloth. They must be kept
spotlessly clean.
Big-end bearing
oil clearance check
3Clean the back side of the new upper
bearing insert, then lay it in place in the
connecting rod. Make sure the tab on the
bearing fits into the recess in the rod so the oil
holes line up. Don’t hammer the bearing insert
into place and be very careful not to nick or
gouge the bearing face. Don’t lubricate the
bearing at this time.4Clean the back side of the other bearing
insert and refit it in the rod cap. Again, make
sure the tab on the bearing fits into the recess
in the cap, and don’t apply any lubricant. It’s
critically important that the mating surfaces of
the bearing and connecting rod are perfectly
clean and oil free when they’re assembled.
5Position the piston ring gaps at staggered
intervals around the piston (see illustration).
6Slip a section of plastic or rubber hose over
each connecting rod cap bolt.
7Lubricate the piston and rings with clean
engine oil and attach a piston ring compressor
to the piston. Leave the skirt protruding about
1/4-inch to guide the piston into the cylinder.
The rings must be compressed until they’re
flush with the piston.
8Rotate the crankshaft until the number one
connecting rod journal is at BDC (bottom
dead centre) and apply a coat of engine oil to
the cylinder wall.
9With the word FRONT (or the arrow) on top
of the piston facing the front of the engine
(see illustration), gently insert the piston/
connecting rod assembly into the number one
cylinder bore and rest the bottom edge of the
ring compressor on the engine block.
10Tap the top edge of the ring compressor
to make sure it’s contacting the engine block
around its entire circumference.11Gently tap on the top of the piston with
the end of a wooden hammer handle (see
illustration) while guiding the end of the
connecting rod into place on the crankshaft
journal. The piston rings may try to pop out of
the ring compressor just before entering the
cylinder bore, so keep some downward
pressure on the ring compressor. Work
slowly, and if any resistance is felt as the
piston enters the cylinder, stop immediately.
Find out what’s hanging up and fix it before
proceeding.
Caution: Do not, for any reason, force the
piston into the cylinder - you might break a
ring and/or the piston.
12Once the piston/connecting rod assembly
is installed, the big-end bearing oil clearance
must be checked before the rod cap is
permanently bolted in place.
13Cut a piece of the appropriate size
Plastigauge slightly shorter than the width of
the big-end bearing and lay it in place on the
number one connecting rod journal, parallel
with the journal axis (see illustration).
14Clean the connecting rod cap bearing
face, remove the protective hoses from the
connecting rod bolts and refit the rod cap.
Make sure the mating mark on the cap is on
the same side as the mark on the connecting
rod. Check the cap to make sure the front
mark is facing the timing chain of the engine.
15Apply a light coat of oil to the under sides
of the nuts, then refit and tighten them to the
torque listed in this Chapter’s Specifications,
Engine removal and overhaul procedures 2B•17
2B
25.13 Lay the Plastigauge strips on each
big-end bearing journal, parallel to the
crankshaft centreline
3261 Jaguar XJ6
25.5 Stagger the ring end gaps around the
piston as shown25.9 Pistons must be installed with the
arrow (right arrow) or FRONT facing the
front of the engine - left arrow indicates
piston size letter
25.11 The piston can be driven (gently)
into the cylinder bore with the end of a
wooden or plastic hammer handle
A Oil ring rail gaps
B Second compression ring gap
C Oil ring spacer gap
D Top compression ring gap

working up to it in three steps. Note:Use the
old bolts for this step (save the new bolts for
final refitting).Use a thin-wall socket to avoid
erroneous torque readings that can result if
the socket is wedged between the rod cap
and nut. If the socket tends to wedge itself
between the nut and the cap, lift up on it
slightly until it no longer contacts the cap. Do
not rotate the crankshaft at any time during
this operation.
16Remove the nuts and detach the rod cap,
being careful not to disturb the Plastigauge.
17Compare the width of the crushed
Plastigauge to the scale printed on the
envelope to obtain the oil clearance (see
illustration). Compare it to this Chapter’s
Specifications to make sure the clearance is
correct.
18If the clearance is not as specified, the
bearing inserts may be the wrong size (which
means different ones will be required). Before
deciding that different inserts are needed,
make sure that no dirt or oil was between the
bearing inserts and the connecting rod or cap
when the clearance was measured. Also,
recheck the journal diameter. If the Plastigauge
was wider at one end than the other, the journal
may be tapered (refer to Section 19).
Final connecting rod refitting
19Carefully scrape all traces of the
Plastigauge material off the rod journal and/or
bearing face. Be very careful not to scratchthe bearing, use your fingernail or the edge of
a credit card to remove the Plastigauge.
20Make sure the bearing faces are perfectly
clean, then apply a uniform layer of clean
moly-base grease or engine assembly lube to
both of them. You’ll have to push the piston
higher into the cylinder to expose the face of
the bearing insert in the connecting rod, be
sure to slip the protective hoses over the
connecting rod bolts first.
21At this time, remove the original
connecting rod bolts/nuts and replace them
with new bolts/nuts. They are of a design
which requires they be used only once. The
old ones are OK for Plastigauge checking, but
for final assembly use only new connecting
rod bolts/nuts. Refit the rod cap and tighten
the nuts to the torque listed in this Chapter’s
Specifications. Again, work up to the torque in
three steps.
22Repeat the entire procedure for the
remaining pistons/connecting rod assemblies.
23The important points to remember are:
a) Keep the back sides of the bearing inserts
and the insides of the connecting rods and
caps perfectly clean during assembly..
b) Make sure you have the correct piston/
connecting rod assembly for each
cylinder.
c) The dimple on the piston must face the
front of the engine.
d) Lubricate the cylinder walls with clean oil.
e) Lubricate the bearing faces when refitting
the rod caps after the oil clearance has
been checked.
24After all the piston/connecting rod
assemblies have been properly installed,
rotate the crankshaft a number of times by
hand to check for any obvious binding.
25As a final step, the connecting rod
endplay must be checked. Refer to Section 13
for this procedure.
26Compare the measured endplay to this
Chapter’s Specifications to make sure it’s
correct. If it was correct before dismantling
and the original crankshaft and connecting
rods were reinstalled, it should still be right.
However, if new connecting rods or a new
crankshaft were installed, the endplay may beinadequate. If so, the connecting rods will
have to be removed and taken to an
automotive machine workshop for resizing.
26 Initial start-up
and running-in after overhaul
1
Warning: Have a suitable fire
extinguisher handy when starting
the engine for the first time.
1Once the engine has been installed in the
vehicle, double-check the engine oil and
coolant levels.
2With the spark plugs out of the engine and
the ignition system and fuel pump disabled,
crank the engine until oil pressure registers on
the gauge or the light goes out.
3Refit the spark plugs, hook up the plug
leads and restore the ignition system and fuel
pump functions.
4Start the engine. It may take a few
moments for the fuel system to build up
pressure, but the engine should start without
a great deal of effort.
5After the engine starts, it should be allowed
to warm up to normal operating temperature.
While the engine is warming up, make a
thorough check for fuel, oil and coolant leaks.
6Shut the engine off and recheck the engine
oil and coolant levels.
7Drive the vehicle to an area with no traffic,
accelerate from 30 to 50 mph, then allow the
vehicle to slow to 30 mph with the throttle
closed. Repeat the procedure 10 or 12 times.
This will load the piston rings and cause them
to seat properly against the cylinder walls.
Check again for oil and coolant leaks.
8Drive the vehicle gently for the first
500 miles (no sustained high speeds) and
keep a constant check on the oil level. It is not
unusual for an engine to use oil during the
running-in period.
9At approximately 500 to 600 miles, change
the oil and filter.
10For the next few hundred miles, drive the
vehicle normally. Do not pamper it or abuse it.
11After 2000 miles, change the oil and filter
again and consider the engine run-in.
2B•18 Engine removal and overhaul procedures
25.17 Measure the width of the crushed
Plastigauge to determine the big-end
bearing oil clearance
3261 Jaguar XJ6

temperature INCREASES, the resistance
values will DECREASE. A failure in this sensor
circuit should set a Code 3 (1988 and 1989)
or 13 (1990 to 1994). This code indicates a
failure in the coolant temperature sensor
circuit, so in most cases the appropriate
solution to the problem will be either repair of
a connector or wire, or renewal of the sensor.
Check
2To check the sensor, measure its resistance
value (see illustration)while it is completely
cold (60 to 80° F = 1500 to 3000 ohms). Next,
start the engine and warm it up until it reaches
operating temperature. The resistance should
be lower (180 to 200° F = 280 to 350 ohms).
3If the resistance values of the coolant
temperature sensor are correct, check the
circuit for the proper signal voltage. Turn the
ignition key ON (engine not running) and
check for reference voltage with a high-
impedance digital voltmeter (see illustration).
It should be approximately 5 volts.
Renewal
Warning: Wait until the engine is
completely cool before
beginning this procedure.
4To remove the sensor, depress the locking
tabs, unplug the electrical connector, then
carefully unscrew the sensor.
Caution: Handle the coolant sensor with
care. Damage to this sensor will affect the
operation of the entire fuel injection
system.
5Before refitting the new sensor, wrap the
threads with Teflon sealing tape to prevent
leakage and thread corrosion.
6Refitting is the reverse of removal.
Oxygen sensor
Note:An oxygen sensor splash shield is
equipped on models from VIN 664941 (mid-1990) to present. This shield prevents the self
diagnosis system from setting an intermittent
and erroneous code 44. Whenever replacing
an oxygen sensor, make sure the splash shield
is in place.
General description
7These models are equipped with a heated
oxygen sensor system. The oxygen sensor is
mounted ahead of the front catalytic converter
and monitors the exhaust gases before they
are changed. The electrical heating system
incorporated into the oxygen sensor allows for
quicker warm-up time and more efficient
oxygen content monitoring. The oxygen sensor
monitors the oxygen content of the exhaust
gas stream. The oxygen content in the exhaust
reacts with the oxygen sensor to produce a
voltage output which varies from 0.1 volts (high
oxygen, lean mixture) to 0.9 volts (low oxygen,
rich mixture). The ECU constantly monitors this
variable voltage output to determine the ratio of
oxygen to fuel in the mixture. The ECU alters
the air/fuel mixture ratio by controlling the pulse
width (open time) of the fuel injectors. A mixture
ratio of 14.7 parts air to 1 part fuel is the ideal
mixture ratio for minimising exhaust emissions,
thus allowing the catalytic converter to operate
at maximum efficiency. This ratio of 14.7 to 1 is
the one which the ECU and the oxygen sensor
attempt to maintain at all times.
8The oxygen sensor produces no voltage
when it is below its normal operating
temperature of about 600° F. During this initial
period before warm-up, the ECU operates in
open loop mode.
9If the engine reaches normal operating
temperature and/or has been running for two or
more minutes, and if the oxygen sensor is
producing a steady signal voltage below
0.45 volts at 1500 or more rpm, the ECU will set
a Code 4 (1988 and 1989) or 26 (1990 to 1994).
10When there is a problem with the oxygen
sensor or its circuit, the ECU operates in theopen loop mode - that is, it controls fuel
delivery in accordance with a programmed
default value instead of feedback information
from the oxygen sensor.
11The proper operation of the oxygen
sensor depends on four conditions:
a) Electrical - The low voltages generated by
the sensor depend upon good, clean
connections which should be checked
whenever a malfunction of the sensor is
suspected or indicated.
b) Outside air supply - The sensor is
designed to allow air circulation to the
internal portion of the sensor. Whenever
the sensor is removed and installed or
renewed, make sure the air passages are
not restricted.
c) Proper operating temperature - The ECU
will not react to the sensor signal until the
sensor reaches approximately 600° F.
This factor must be taken into
consideration when evaluating the
performance of the sensor.
d) Unleaded fuel - The use of unleaded fuel
is essential for proper operation of the
sensor. Make sure the fuel you are using
is of this type.
12In addition to observing the above
conditions, special care must be taken
whenever the sensor is serviced.
a) The oxygen sensor has a permanently
attached pigtail and electrical connector
which should not be removed from the
sensor. Damage to or removal of the
pigtail or electrical connector can
adversely affect operation of the sensor.
b) Grease, dirt and other contaminants
should be kept away from the electrical
connector and the louvered end of the
sensor.
c) Do not use cleaning solvents of any kind
on the oxygen sensor.
d) Do not drop or roughly handle the sensor.
6•4 Emissions and engine control systems
3261 Jaguar XJ6 4.2 The coolant temperature sensor is in the thermostat housing.
To check the coolant temperature sensor, use an ohmmeter to
measure the resistance between the two sensor terminals
4.3 Check for reference voltage to the electrical connector for the
coolant sensor with the ignition key ON (engine not running).
It should be approximately 5.0 volts

28Check the signal voltage from the
potentiometer. Carefully backprobe the
electrical connector on the signal voltage
wire (-) with the ignition key ON (engine not
running) (see illustration). There should be
approximately 0.5 volts.
29Next, rotate the throttle lever manually and
confirm that the reference voltage increases to
approximately 4.8 volts (see illustration).
30If the voltage does not increase, renew
the throttle potentiometer with a new part.
Renewal
31Remove the throttle body from the intake
manifold (see Chapter 4).
32Remove the two mounting bolts and
separate the throttle potentiometer from the
throttle body. Note:The throttle potentiometer
is difficult to reach and adjustment requires
that the home mechanic tighten the bolts after
the final adjustment using a mirror. Be sure to
mark the mounting position of the old throttle
potentiometer before refitting the new part.
33Refitting is the reverse of removal.
Adjustment
34Refit the throttle body with the throttle
potentiometer mounting bolts just looseenough to move the potentiometer. Be sure
the bolts are tight and the potentiometer does
not rotate easily.
35Backprobe the signal wire and the ground
wire (see Step 28) and with the throttle closed
(idle position), rotate the potentiometer until
the voltmeter reads between 0.2 and 0.5 volts.
Note:The throttle potentiometer is difficult to
reach. Be sure to rotate the potentiometer
slowly and do not interfere with the voltmeter
and the electrical connectors to the gauge.
36Rotate the throttle lever and confirm that
the voltage increases to around 4.8 volts.
If the voltage range is correct, the throttle
potentiometer is installed correctly.
37Tighten the throttle potentiometer bolts. If
necessary, use a small mirror to locate the
bolts.
Mass airflow (MAF) sensor
General Information
38The mass airflow sensor (MAF) is located
on the air intake duct. This sensor uses a hot
wire sensing element to measure the amount
of air entering the engine. The air passing over
the hot wire causes it to cool. Consequently,this change in temperature can be converted
into an analogue voltage signal to the ECU
which in turn calculates the required fuel
injector pulse width.
Check
39Check for power to the MAF sensor.
Backprobe the MAF sensor electrical plug.
Working on the harness side with the ignition
ON (engine not running), check for battery
voltage on terminal number 5 (see illustration).
40Remove the pin and backprobe the MAF
sensor electrical connector terminal number 3
with the voltmeter (see illustration). The
voltage should be less than 1.0 volt with the
ignition switch ON (engine not running). Raise
the engine rpm. The signal voltage from the
MAF sensor should increase to about 2.0 volts.
It is impossible to simulate load conditions in
the driveway but it is necessary to observe the
voltmeter for a fluctuation in voltage as the
engine speed is raised. The vehicle will not be
under load conditions but MAF sensor voltage
should vary slightly.
41If the voltage readings are correct, check
the wiring harness for open circuits or a
damaged harness (see Chapter 12).
6•6 Emissions and engine control systems
4.29 . . . then check the SIGNAL voltage
with the throttle wide open. It should be
between 4.5 and 5.0 volts4.39 Check for battery voltage to the MAF
sensor on terminal number 54.40 With the engine idling, raise the engine
rpm and observe the voltage changes on
terminal number 3
3261 Jaguar XJ6 4.27 Backprobe the throttle potentiometer electrical connector
with a pin and with the ignition key ON (engine not running) there
should be 5.0 volts REFERENCE available
4.28 First check the throttle potentiometer SIGNAL voltage with the
throttle closed (idle). It should be 0.2 to 0.5 volts . . .