1997 JAGUAR XJ6 fold seats

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

done during the engine overhaul. Note:If the
engine was severely overheated, the cylinder
head is probably warped (see paragraph 12).
Cleaning
2Scrape all traces of old gasket material and
sealing compound off the cylinder head
gasket, intake manifold and exhaust manifold
sealing surfaces. Be very careful not to gouge
the cylinder head. Special gasket-removal
solvents that soften gaskets and make
removal much easier are available at car
accessory outlets.
3Remove all built up scale from the coolant
passages.
4Run a stiff wire brush through the various
holes to remove deposits that may have
formed in them. If there are heavy deposits in
the water passages, the bare head should be
professionally cleaned at a machine
workshop.
5Run an appropriate-size tap into each of the
threaded holes to remove corrosion and
any thread sealant that may be present. If
compressed air is available, use it to clear the
holes of debris produced by this operation.
Warning: Wear eye protection
when using compressed air!
6Clean the exhaust and intake manifold stud
threads with a wire brush.
7Clean the cylinder head with solvent and dry
it thoroughly. Compressed air will speed the
drying process and ensure that all holes and
recessed areas are clean. Note:Decarbonising
chemicals are available and may prove very
useful when cleaning cylinder heads and valve
train components. They are very caustic and
should be used with caution. Be sure to follow
the instructions on the container.
8Clean the lifters with solvent and dry themthoroughly. Compressed air will speed the
drying process and can be used to clean out
the oil passages. Don’t mix them up during
cleaning - keep them in a box with numbered
compartments.
9Clean all the valve springs, spring seats,
keepers and retainers with solvent and dry
them thoroughly. Work on the components
from one valve at a time to avoid mixing up
the parts.
10Scrape off any heavy deposits that may
have formed on the valves, then use a
motorised wire brush to remove deposits from
the valve heads and stems. Again, make sure
that the valves don’t get mixed up.
Inspection
Note:Be sure to perform all of the following
inspection procedures before concluding that
machine workshop work is required. Make a
list of the items that need attention. The
inspection procedures for the lifters and
camshafts, can be found in Part A.
Cylinder head
11Inspect the cylinder head very carefully for
cracks, evidence of coolant leakage and other
damage. If cracks are found, check with an
automotive machine workshop concerning
repair. If repair isn’t possible, a new cylinder
head should be obtained.
12A common problem on aluminium engines
is erosion of the cylinder head or engine block
coolant passages due to improper sealing.
Using a new cylinder head gasket held
against the cylinder head, trace the bolt holes
and coolant passage outlines in pencil on the
cylinder head. Use the gasket to trace the
same on the top of the engine block (see
illustration). If the top of the engine block has
eroded outsideof the pattern around thewater passages or cylinder head bolt holes,
the engine block must be renewed; the
manufacturer doesn’t recommend resurfacing
it. If the cylinder head has eroded outside of
the water passage holes but the erosion is
away fromthe combustion chamber, the
eroded area can be built up with metal-
impregnated epoxy and machined flat again.
13Using a straightedge and feeler gauge,
check the cylinder head gasket mating
surface (on the engine block and cylinder
head) for warpage (see illustration). If the
warpage exceeds the limit found in this
Chapter’s Specifications, it can be resurfaced
at an automotive machine workshop, but no
more then 0.010-inch of material should be
removed. If the cylinder head had been
overheated, take it to the machinist for
inspection before proceeding further. It’s
possible that the overheating could have
annealed (softened) the aluminium of the
cylinder head, making it unsuitable for
machine work. In this case, a new cylinder
head is required.
Note 1:To check if a cylinder head has been
machined previously, measure the height
between the cylinder head gasket surface and
the valve cover mounting surface with a large
micrometer or vernier caliper and compare
with Specifications.
Note 2:Jaguar aluminium cylinder heads
require precision machine work. It is best to
find a machine workshop that has
considerable experience in servicing Jaguar
cylinder heads.
14Examine the valve seats in each of the
combustion chambers. If they’re pitted,
cracked or burned, the cylinder head will
require valve service that’s beyond the scope
of the home mechanic.
Engine removal and overhaul procedures 2B•7
2B
3261 Jaguar XJ6 10.12 Place the new head gasket on the engine block, and trace
around the water passages and bolt holes - make sure there is no
erosion of the aluminium beyond these lines
10.13 Check the cylinder head and engine block gasket surfaces
for warpage by trying to slip a feeler gauge under a precision
straightedge (see the Specifications for the maximum warpage
allowed and use a feeler gauge of that thickness) - check both the
cylinder head and engine block (shown)