100-04-39 Noise, Vibration and Harshness 100-04-39
DIAGNOSIS AND TESTING (CONTINUED)
E859 EN 02/2001 2002 Bantam
Road Test
A gear-driven unit will produce a certain amount
of noise. Some noise is acceptable and may be
audible at certain speeds or under various driving
conditions, as on a new asphalt road. The slight
noise is in no way detrimental and must be
considered normal.
The road test and customer interview (if
available) provide information needed to identify
the condition and give direction to the correct
starting point for diagnosis.
1. Make notes throughout the diagnosis routine.
Use a Road Test form that includes space for
comments. Make sure to write down even the
smallest bit of information, because it may
turn out to be the most important.
2. Do not touch anything until a road test and a
thorough visual inspection of the vehicle
have been carried out. Leave the tyre
pressures and vehicle load just where they
were when the condition was first observed.
Adjusting tyre pressures, vehicle load or
making other adjustments may reduce the
conditions' intensity to a point where it cannot
be identified clearly. It may also inject
something new into the system, preventing
correct diagnosis.
3. Make a visual inspection as part of the
preliminary diagnosis routine, writing down
anything that does not look right. Note tyre
pressures, but do not adjust them yet. Note
leaking fluids, loose nuts and/or bolts, or
bright spots where components may be
rubbing against each other. Check the
luggage compartment for unusual loads.
4. Road test the vehicle and define the
condition by reproducing it several times
during the road test.
5. Carry out the Road Test Quick Checks as
soon as the condition is reproduced. This will
identify the correct diagnostic procedure.
Carry out the Road Test Quick Checks more
than once to verify they are providing a valid
result. Remember, the Road Test Quick
Checks may not tell where the concern is,
but they will tell where it is not.
Road Test Quick Checks
1. 24-80 km/h (15-50 mph): With light
acceleration, a moaning noise is heard and
possibly a vibration is felt in the front floor
pan. It is usually worse at a particular engine
speed and at a particular throttle setting
during acceleration at that speed. It may also
produce a moaning sound, depending on
what component is causing it.
Refer to Tip-In
Moan in the Symptom Chart.
2. Acceleration/Deceleration: With slow
acceleration and deceleration, a shake is
sometimes noticed in the steering
wheel/column, seats, front floor pan, front
door trim panel or front end sheet metal. It is
a low frequency vibration (around 9-15 cycles
per second). It may or may not be increased
by applying brakes lightly.
Refer to Idle
Boom/Shake/Vibration in the
Symptom
Chart.
3. High Speed: A vibration is felt in the front
floor pan or seats with no visible shake, but
with an accompanying sound or rumble,
buzz, hum, drone or booming noise. Coast
with the clutch pedal depressed and engine
idling. If vibration is still evident, it may be
related to wheels, tires, front brake discs,
wheel hubs or front wheel bearings. Refer to
High Speed Shake in the Symptom Chart.
4. Engine rpm Sensitive: A vibration is felt
whenever the engine reaches a particular
rpm. It will disappear in neutral coasts. The
vibration can be duplicated by operating the
engine at the concern rpm while the vehicle
is sitting still. It can be caused by any
component, from the accessory drive belt to
the clutch, which turns at engine speed when
the vehicle is stopped. Refer to Engine
Accessory Vibration in the Symptom Chart.
5. Noise and Vibration While Turning: Clicking,
popping, or grinding noises may be due to
the following:
• Cut or damaged front wheel halfshaft joint
boot resulting in inadequate or contaminated
lube fill in the outboard front wheel halfshaft
joint or inboard front wheel halfshaft joint.
• Loose front wheel halfshaft joint boot clamp.
• Other component contacting the halfshaft
assembly.
• Worn, damaged, or incorrectly installed front
wheel bearing.
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