Pickup 2WD L4-2350cc 2.4L SOHC 8 Valve (1996)
Doors: Technical Service Bulletins
Interior - Wind Noise Diagnosis
NO.: TSB-97-42A-001
DATE: February, 1997
MODEL: All Models
SUBJECT:
WIND NOISE DIAGNOSIS
PURPOSE
As vehicle interiors become quieter, wind noise becomes more noticeable to the customer. Modern sealing techniques and smooth aerodynamic exteriors
significantly reduce the causes of wind noise. Customer expectations of interior quietness require technicians to detect and correct even small wind
noises. This bulletin describes common causes of wind noise and how to diagnose them.
Specific corrective actions may vary from model to model.
AFFECTED VEHICLES
All Mitsubishi models
CAUSES OF WIND NOISE
Wind noise may be created by:
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Air turbulence as air flows over the vehicle
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Aspiration as air enters or leaves the interior
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Vibration of a vehicle part from force of air flowing over it
Air Turbulence
When air flows smoothly over a moving object, no noise is produced. If the smooth flow of air is disturbed by an edge, gap or projection, the air flow
becomes turbulent and creates wind noise.
Aspiration
When a pressure difference exists between two spaces (such as between a vehicle's interior and exterior), any opening will allow air to move from a high
pressure space to a lower pressure space. As the air flows from one space to another, aspiration noise is created. Common causes of aspiration noise are
loose weatherstripping and partially open sunroof, doors or windows. Aspiration noise varies with vehicle speed and ventilation blower speed.
Vibration
Wind noise can also be caused by air flowing over a vehicle part and causing it to vibrate. Vibrating air intake grilles made of thin bars, radio antennas,
outside mirrors, and loose or protruding body mouldings are common causes of wind noise.
DIAGNOSIS PROCEDURES
1.
Ask the customer for details about the apparent location of the noise and the conditions under which the noise occurs. Try to determine the vehicle
speed, weather conditions, and wind direction.
2.
Test drive the vehicle under similar conditions with the customer. The technician should sit in the appropriate seat where the wind noise is most
audible.
3.
A stethoscope, ultrasonic leak detector or smoke generator can assist in detecting the source of an aspiration type of wind noise. A smoke
generator and ultrasonic leak detector can be used when the vehicle is not moving.
NOTE:
Leak detectors and smoke generators cannot identity wind noise created by vibrating mouldings, air intake grilles or antennas. Diagnose this type of
noise during test drives.
a.
Leak detectors have a sound wave emitter and a receiver. Hold the emitter inside the vehicle with the doors closed. Sound waves from the
emitter are picked up by a receiver being held outside the vehicle. Any gap in the vehicle's sealing provides a path for the sound waves to
travel through.
b.
With the heater/air conditioning blower on the highest setting with the outside air circulating, hold a smoke generator outside the vehicle
near a suspected air leakage area. Visible air flow inside the vehicle will reveal where air leaks exist. Good light and calm air are important
when using this method.
4.
Determine whether any accessories or other easily removed parts could cause wind noise by vibrating as air flows over them. Antennas and roof
