Jaguar XJ (X350). Manual — part 38

Lift Test

After a road test, it is sometimes useful to do a similar test on a lift.

When carrying out the high-speed shake diagnosis or engine accessory vibration diagnosis on
a lift, observe the following precautions:

WARNING: If only one drive wheel is allowed to rotate, speed must be limited to

55 km/h (35 miles/h) indicated on the speedometer since actual wheel speed will be twice
that indicated on the speedometer. Speed exceeding 55 km/h (35 miles/h) or allowing the
drive wheel to hang unsupported could result in tire disintegration, differential failure,
constant velocity joint and driveshaft failure, which could cause serious personal injury
and extensive vehicle damage. Failure to follow these instructions may result in personal
injury.

CAUTION: The suspension should not be allowed to hang free. When the CV

joint is run at a very high angle, extra vibration as well as damage to the seals and joints
can occur.

The rear suspension lower arm should be supported as far outboard as possible. To bring the
vehicle to its correct ride height, the full weight of the vehicle should be supported in the rear
by floor jacks. <<100-02>>

1 . Raise and support the vehicle. <<100-02>>

2 . Explore the speed range of interest using the Road Test Quick Checks as previously
described.

3 . Carry out a coast down in neutral. If the vehicle is free of vibration when operating at a
steady indicated speed and behaves very differently in drive and coast, a transmission concern
is likely.

Note, however, that a test on the lift may produce different vibrations and noises than a road
test because of the effect of the lift. It is not unusual to find vibrations on the lift that were not
found in the road test. If the condition found on the road can be duplicated on the lift, carrying
out experiments on the lift may save a great deal of time.

Symptom Chart

High-speed shake

Possible Source(s):

•

Wheel end vibration.

•

Engine/transmission.

•

Driveline.

Action(s) to take:

•

GO to Pinpoint Test A.

Tip-in moan

Possible Source(s):

•

Air cleaner.

•

Power steering (PS).

•

Powertrain.

•

Engine mounts.

•

Exhaust system.

Action(s) to take:

•

GO to Pinpoint Test B.

Idle boom/shake/vibration, or
shudder

Possible Source(s):

•

Cable(s)/hoses(s).

•

Engine mounts.

•

Exhaust system.

•

Belt/pulleys.

Action(s) to take:

•

GO to Pinpoint Test C.

Wheel end vibration analysis

Possible Source(s):

•

Suspension/rear drive half shaft and CV joints.

•

Tires/wheels.

•

Wheel bearings.

•

Rear wheel drive half shaft joint boots.

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Action(s) to take:

•

GO to Pinpoint Test D.

Non-axle noise

Possible Source(s):

•

Trim/mouldings.

•

A/C system.

•

Accessories.

•

Air suspension system.

Action(s) to take:

•

GO to Pinpoint Test E.

Pinpoint Tests

NOTE:

These Pinpoint Tests are designed to take the technician through a step-by-step diagnosis
procedure to determine the cause of a condition. It may not always be necessary to follow
the chart to its conclusion. Carry out only the Pinpoint Test steps necessary to correct the
condition. Then check operation of the system to make sure the condition is corrected.

After verifying that the condition has been corrected, make sure all components removed have
been installed.

PINPOINT TEST G215673p1 : HIGH-
SPEED SHAKE

G215673t2 : NEUTRAL COAST

1. Carry out the neutral coast test.

•

Does the vibration disappear during the neutral coast test?

-> Yes
CHECK and INSTALL new engine/transmission mounts as necessary. REPEAT Road Test as
outlined.

-> No
GO to Pinpoint Test G215673t10.

PINPOINT TEST G215673p2 : TIP-IN
MOAN

G215673t3 : CHECK THE AIR CLEANER

1. Check the air cleaner.

Check the air cleaner, inlet tube, outlet tube, resonators and all other components associated
with the air induction system for correct installation and tightness of all connections.

•

Are the components OK?

-> Yes
GO to Pinpoint Test G215673t4.


-> No
CORRECT the condition. REPEAT the Road Test as outlined.

G215673t4 : CHECK THE EXHAUST SYSTEM

1. Carry out the exhaust system neutralizing procedure in this section.

•

Is the exhaust system OK?

-> Yes
GO to Pinpoint Test G215673t5.


-> No
REPAIR as necessary. RESTORE vehicle. REPEAT the Road Test as outlined.

G215673t5 : CHECK THE POWER STEERING

1. Remove the auxiliary drive belt and test for tip-in moan.

•

Is the tip-in moan OK?

-> Yes
REPAIR the power steering as necessary. For additional information, refer to <<211-02>>

-> No
CHECK and INSTALL new engine/transmission mounts as necessary. REPEAT Road Test as
outlined.

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