9 - Suspension & Steering ( ,
The Jaguar suspension is renowned for itís ability to provide a luxury ride whilst also offering a degree of grip and handling not normally associated with this class of vehicle.
The basic layout is unchanged since the later XJ40 models, though there are changes to the rear suspension relative to earlier XJ40ís, which makes changing the rear shock absorbers a more complex task.
9.1 - Front Shock Absorber Replacement Bushings ( ,
The bushings are a known weak point, particularly on the left side of the car where heat from the coolant header tank is thought to affect them.
Feel above shock at top of body. If the bushing is deformed, or there is space then you probably have a half or three quarter inch of travel before the shick absorber begins to work. There will probably also be a bump as it hits the body work. This tends to be more of a problem on the left hand side of the car, due to the proximity of the coolant header tank.
It is vital to be really careful when replacing the bushes or shock absorbers - the warning next to top shock absorber mount is not there for nothing! The shock absorber is only thing which holds the spring in place, so the risk is that if the lower suspension drops too far, then the spring can come out sideways with a lot of energy and cause serious injury.
To perform the task, first slightly loosen, but do not remove, the top locknut, using a vice grip or similar if necessary in the top of the wheelarch to stop the shock absorber rod turning. Put the car up on a stand and then raise the lower suspension arm using a jack near the balljoint and then use a second stand or similar to raise up the suspension a little and so prevent the spring escaping.
If replacing the shock absorber itself, undo the nut and bolt attaching the lower end of the unit to the lower control arm. This is not necessary if just the bushings are being replaced.
Now undo the top shock absorber mount and depress the shock absorber rod itself. The existing bushing can now be removed and replaced as, where appropriate, can the shock absorber itself.
Refit the new components and tighten the top mount and, if necessary, lower mounting bolt, before releasing the suspension.
If you are not changing the shocks, and have had to use a vice to hold the rod, ensure the rod does not have any damage or burrs on it, as these will damage the seals of the shock itself when in use.
9.2 - Wheel Bearing Check and Adjustment ( ,
A quick check can be made with the appropriate wheel jacked off the ground. There should be no movement with the wheel grasped horizontally, but a small degree of movement appears normal with the wheel grasped vertically.
A loose or tight bearing will wear more rapidly than a correctly adjusted one. A loose bearing will also cause a degree of wander and sloppiness in the steering.
To adjust the bearing, remove the wheel and prise off the protective centre cap with a screwdriver. Straighten the bent ends of the cotter pin and remove using a pair of long nose pliers. The pin can be reused provided it is not obviously weakened.
Remove the locknut, nut and washer from the spindle. Pull the hub out slightly to move the outer bearing on the spindle.
Gently push the hub back and refit the washer and nut. Initially only hand tighten the nut. Fit a torque wrench and rotate the wheel in the forward direction whilst gradually tightening to 20lb ft.
Now loosen the nut a quarter turn and retighten by hand. Only use a socket to tighten a fraction more if necessary in order to be able to refit the locking nut and cotter pin.
Bend the ends of the cotter pin to lock it in place, then refit the centre dust cap
9.3 - Wheel Alignment ( ,
This is a frequent source of problems on the Jaguar, as the correct factory procedure for tracking alignment requires that the suspension is pre-loaded ( ie. Tied down with a known force ) before the adjustment is made. Few garages are aware of this and therefore almost always set excessive toe-out.
Excessive toe-out produces vague steering, tramlining and excessive wear on the inside edges of the front tyres. By contrast, toe-in causes wear on the outer edges of the tyres and produces a stronger self-centring effect on the steering.
It is possible to adjust the tracking yourself, but be aware that getting it wrong is expensive on tyres and can greatly impair handling. Also be aware that wear in other suspension components may produce similar symptoms.
Lift the front of the car and locate the tie rods leading from the rear of the front hub assembly to the steering rack. The rods are threaded such that turning them clockwise effectively shortens them, moving the rear of the wheels closer together therefore producing toe-out. Turning anticlockwise produces toe-in.
Use a spanner to hold the rod in position whilst undoing the lock nut. Turn the rod as necessary then retighten the lock nut. Experience suggests that a typical excessive toe-out can be corrected by turning the track rod anticlockwise by one to two flats, but be aware this may not work for you.