The
XJ6 Jaguar
Front
Suspension
Front Disk
Brakes
Many people are intimidated by suspension work. On the
Jaguar there is no real reason to be. The suspension is
straight forward and easy to work on if you have a good
manual and the proper tools.
The front disc brakes are also in this area and I will
start with some comments on them. If you are experiencing a
terrible shaking when you brake from high speed and you have
been blaming it in the front suspension, try the brakes
first. The brakes are easier to work on and cheaper to
repair and when all is said and done, the front suspension
is probably not the culprit. The most likely problem is
warped front discs. Even if they are fairly new they can be
warped and it does not take much to cause a real wild shake.
The usual cause of warped discs is a rapid cooling after
being overheated. This can happen on the way home from the
dealer with a new car. All it takes is hard braking and a
very cold day or a mud puddle to spray water on the disc
while it is hot.
Luckily it is a very cheap and easy fault to cure. The
removal of the front discs is so simple that it will take
less than 30 minutes per side even on your first attempt.
There are two types of front disc brake calipers on the XJ6.
The removal of the disc is different for the two different
types.
The beginning of the procedure is the same for both
types. After jacking up the car and stabilizing it on stands
the front wheels are removed.
On the cars with the 4 piston calipers it will then be
necessary to remove the calipers so that you can get the
discs off. After removing the calipers they can be tied back
and supported out of the way while still connected to the
brake system. Do not allow the calipers to be supported by
the brake line as this stress can break the line. There is
no need to bleed the system if they are left connected. To
remove them it will be necessary to depress the brake pads
away from the disc. This can be done with a screwdriver as a
pry bar. They only need to be pushed back enough to slide
the caliper off the disk. When doing this the excess brake
fluid is pushed up into the reservoir. It may be necessary
to remove some of the fluid to prevent it running over. When
the calipers are removed it is necessary to note the
position of all shims between the steering arm and the
caliper. Be sure there are none still sticking to the
caliper that will fall off later and leave you wondering
where they came from. They must be put back on just as you
found them.
On cars with the three piston calipers the calipers do
not need to be removed. It is only necessary to remove the
brake pads. As in the previous paragraph it is only
necessary to spread the pads slightly and then they can be
removed.
Now you can check the runout with a dial gauge or by
using a feeler gauge and a fixed point to measure to. The
dial gauge is the easiest and most reliable. The runout
should not exceed one tenth of a millimeter. If it does they
need truing up.
If you are going to continue to remove the disc (the
runout was excessive) on both types, remove the dust cover
from the axle end, remove the cotter pin and remove the nut
and thrust washer from the end of the axle. Do not, as some
books will tell you, unbolt the hub from the disk. It isn't
necessary and its a hell of a job if it is still on the axle
because you have to feel around through a hole in the
backing plate to get to the bolts. It is much easier to
separate the two with the hub and disk on the bench where
you can get to it. The disc and hub can now be slid off the
end of the axle and out from under the caliper.
Put the whole thing on the bench and separate the hub
from the disc. By doing the job on the bench instead of on
the car you can get the bolts torqued down properly when you
reassemble the two. On the car it is virtually
impossible.
After the discs are removed take them to a shop and have
them turned for pocket change. Remount the discs and your
shaking front end will be cured. If it isn't, then you need
to then check out the ball joints etc. You needed to
resurface those discs anyway and it didn't cost much.
When you put the wheels back on, don't forget to use some
anti-seize on the hub and on the lug bolts. Jaguar wheels
being of different metal than the hubs are prone to seize
and be difficult to remove. If you do have a stuck wheel the
best solution is to put pressure on the bottom of the wheel
by prying against the lower ball joint mounting in the front
or a similar spot in the rear.
Front End
Geometry
The front end geometry of the Jaguar is very simple if
you understand what they are trying to do. There are three
terms that need to be explained first. These are castor,
camber and toe in.
Castor is the fore and aft tilt of the axis about which
the front steering is rotated. If the castor is positive
(the axis is tilted forward at the top toward the direction
the car is traveling) the car will be stable and tend to run
in a straight line. If the castor is negative (the bottom of
the axis is forward of the top of the axis) then the car
will be unstable and want to run to one side or the other of
the road. Thus the castor must always be positive for
safety. The amount of positive castor determines, to an
extent, the energy needed to turn the car . If the castor is
too much positive then the car will require more work to
turn it away from the straight line and it will return to a
straight line very quickly. This should be avoided. If the
castor is not enough then the steering will feel light and
"squirly". Race cars usually use less castor than street
cars since they want a very light touch to the steering. The
castor is adjustable using shims in front of and behind the
upper ball joint. ALWAYS when removing the upper ball joint,
take note of the number and position of the shims and put
them back where you found them. You will have to take it to
a front end shop later to have it checked, but always start
where it was before the repair.
Camber is the outward tilt of the wheel as looked at from
the front of the car. A positive camber means the top of the
wheel tilts to the outside and the bottom of the wheel seems
to point in. Slight positive camber is desired as the camber
will decrease toward negative as the weight of the car is
increased such as when going around a banked turn. Camber
can affect the wear on the tires and the stability during
cornering. The camber is adjusted using shims on the inside
mounting end of the upper wishbone arms. Again whenever
disturbing them, note where they were and replace them then
get a fresh alignment.
The toe in is the tendency of the tires to look toward
each other as crossed eyes. The front of the tire looks in.
Since toe in decreases with speed it is desired to have a
slight "static" toe in. At road speed the toe in may be
neutral, if it is correctly adjusted, thus maximizing tread
life. The toe in is adjusted by adjusting the length of the
tie rod. This is one adjustment you can do at home with a
ruler but I don't recommend it since it affects your tire
wear. The cost of a professional alignment is about the cost
of one tire but without it you will wear all four tires
unnecessarily.
The entire system consists of the upper wishbone, the
lower wishbone, the body of the car and the stub axle. These
four components make up a rectangle. The idea being that as
the load on the wheel increases or decreases the wheel will
essentially stay straight up and down as it moves up and
down. This as opposed to how the older VW swing axles
allowed the camber to vary from very negative under heavy
load and very positive under light load. The ball joints
allow the wheel to turn right or left as they are pushed by
the tie rod which is in turn connected to the steering.
Upper Ball
Joints
I will not go into the exact procedure for working on the
front suspension since I will assume that you have a proper
manual. If you don't, get one. This book is not meant to
replace a manual, only to educate you to the general ease
with which you can maintain your own car. I will however
tell you of one thing I did not find in the Haynes manual
when I put in upper ball joints.
When I put the new one in I made the mistake of
tightening the nut on the ball joint that fastens it to the
stub axle upright of the wheel. The manual did not warn
against that. Once it is tightened it is almost impossible
to loosen unless the two horizontal bolts into the
suspension arm have already been installed. And if they
haven't it is next to impossible to compress the rubber
stoppers enough to get them in. Catch 22! So, don't tighten
the nut at first!
Instead, place the nut on the end of the tapered shaft
just enough to hold the stub axle upright together, place
the two horizontal bolts into the ball joint, then, and only
then, tighten the ball joint to the stub axle upright.
Andrew Kalman offers the following suggestions when
replacing the upper and lower ball joints:
"1) If you choose to do the job without removing the
brake lines, calipers or rotors, make sure you have a nice,
steady means of supporting this assembly without putting
stress on the brake lines. I did it this way, and saved some
time, but it's more aggravating than having the whole unit
off.
Careful -- this hub / rotor / brake assembly is
heavy!
2) Disconnect the anti-sway bar.
3) You will need a small tie-rod separator, the kind that
pushes with a screw against the object held by two
"grabbers". I rented one at Grand Auto for a few bucks to do
the upper one - for the lower one I used a similar type, but
with moveable jaws. It's pretty tight in there. I could
hardly believe how much force was needed to pop the joints
loose.
4) I did not remove the _metal_ lipped cup (C 30952) from
the lower ball joint "body" - in retrospect, using an XJ-40
lower ball joint would have been better. I used a Dremel
tool to cut out the phenolic cup (one radial cut).
5) The upper ball joint is much easier to deal with.
6) You'll find a jack quite handy in repositioning the
front suspension while disassembling and reassembling.
7) After a few miles re-check the circlips that hold the
rubber boots on - one of mine "walked"."
The lower ball joints are adjustable to get the desired
clearance in the socket. The adjustment is done using shims.
The newer XJ40 lower ball joints are said to be an exact
replacement for the earlier XJ6 lower balljoints.
The upper ball joint is only replaceable, there is no
adjustment when it gets worn.
Another area where wear occurs and can cause a loose
front end is the inner bushes on the upper and lower
wishbone mountings. The upper bushes are especially prone to
wear. You can replace all of these yourself with a good
manual and tools such as a spring compressor.
In Bela Orbans APPENDIX ON FRONT END REPAIR at the end of
this book you will learn about the little bits of rubber on
the Anti-roll bar and the inner bushes of the upper and
lower wishbones.
Steering Rack
Bushings
The steering rack bushings are a source of alot of
looseness in the steering of the XJ6. When they get old and
worn the steering can get very loose.
From Julio Loza I received the following advice on
replacing the steering rack bushings.
"The other suggestion I have is for changing the infamous
steering rack bushings on the XJ6 with polyurethane ones.
While doing this job, I found that there is a metal sleeve
on the original bushings. It was not obvious at first that
they were there since the metal sleeve looked like it could
have been part of the steering rack. Only after I compared
the size of the new bushings( which come with no metal
sleeve ) and the rack mount holes did I realize that these
must be sleeves. Since they were tight in place and could
not be removed, I took a saw to them. I cut two lines along
the sleeves that release the pressure and allowed me to
punch them out with a punch and hammer. Care must be taken
when sawing so that you saw through the sleeve but not the
steering rack itself."
Kirby Palm warns that cutting the sleeve out can be
dangerous especially if it is still on the car. If you so
much as nick the aluminum lug it can cause it to crack
later. He suggests that cutting them should be a last
resort. Kirby suggests first trying two 3/8" drive sockets,
one the same OD as the bushing and one large enough that the
bushing will fit inside it. Thread a 3/8" bolt through the
two then draw it tight with a nut to pull the bushing
out.
Grease Points
When maintaining the front end there are 9 grease points
that need attention on a regular basis to prevent wear. The
upper and lower ball joints all have a grease fitting unless
the upper ball joints have been replaced. Some replacement
upper balljoints are "lifetime" lubricated. I don't know
whose lifetime, but they don't come with a grease nipple.
There is a grease nipple on both the wheel hubs and on both
the tie rod ends. The last grease nipple is on the steering
rack.
On to the
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