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.
Front
Suspension Overview
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.
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
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
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.
Toe-in
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.
Front
Disc Brakes
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.
Removing
the Front Brakes
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: 4 piston claipers and
3 piston calipers. 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.
Four Piston Calipers
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 disc. 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.
Three Piston Calipers
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 disc. 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 disc 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.
Fitting the Wheels
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.
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:
- 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!
- Disconnect the anti-sway bar.
- 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.
- 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).
- The upper ball joint is much easier to deal with.
- You'll find a jack quite handy in repositioning the front
suspension while disassembling and reassembling.
- 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.
Wishbone
Mounting Bushes
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.
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.
Polyurethane
Bushings
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
inch drive sockets, one the same OD as the bushing and one large
enough that the bushing will fit inside it. Thread a 3/8 inch 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.
Next is
the Interior
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