Professional_Tool_And_Equipment_News_September_2019 - 38

Diagnosing NVH
Understanding the different types of noises, what can cause them, and the appropriate
methods to find the source are essential in diagnosing noise, vibration, harshness issues.
By Barry Hoyland, Contributing Editor

oise, vibration, harshness (NVH) issues can be time-consuming to diagnose.
This is mainly because noise and vibrations can use the vehicle's structure
(chassis) as an antenna to transmit the noise throughout the vehicle, making
it difficult to pinpoint the exact cause of a noise.
Additionally, noises can be caused by
noise reduction headphones and superb
worn components in just about any sysmicrophone, makes it much easier to
tem or by wind passing over or through
identify specific noises.
the vehicle. Let's start off by explaining
If the growling noise is not present
with
the vehicle stationary, then the
different types of noises and their possible causes, then we will discuss the best
noise can become a little more difficult to
tools to use to find the source of a noise.
locate. Rotational noises that are present
As always, use your vehicle informawith vehicle movement can be caused by
tion source to determine if there are any
bearings in the transmission, axles, hubs,
technical service bulletins (TSBs) related
or differential. These noises can also be
to the issue the vehicle is having. You
caused by worn gears in the transmission
should also be aware that there are some
excellent diagnostic procedures available
for isolating and locating noise or vibration issues on a vehicle in ALLDATA's
information database.

TOOLS USED:
* Vehicle Information
* Scan Tool
* JS Products Steelman
EngineEAR Stethoscope
* JS Products Steelman
Wireless ChassisEAR
Diagnostic Device Kit
* Ultrasonic Leak Detector
* Diagnostic Smoke Tester

GROWLING OR
HOWLING NOISES

Typically, a growling noise is caused by
a worn bearing. If the noise occurs when
the engine is running and the vehicle is
stationary, it is due to an engine-driven
component. The noise level may be
constant or change with engine speed.
Engine-driven components include water
and power steering pumps, belt idlers
and tensioners (including timing belt
components), alternators, and air conditioning compressors. Some of these
parts can be isolated by turning them
off or removing a belt to determine if
the noise is eliminated. In other cases,
an electronic stethoscope, such as the
Steelman EngineEAR, can be used to
locate the source of the noise.
Use the stethoscope to listen to individual components in order to isolate the
noise. The EngineEAR has the capability of adjusting the volume of the microphone. This feature, coupled with its

PTEN

SEPTEMBER 2019

p Place each ChassisEAR microphone near the suspected noise, keeping each microphone/transmitter
approximately the same distance from the suspect parts.

www.VehicleServicePros.com

http://www.VehicleServicePros.com

Professional_Tool_And_Equipment_News_September_2019

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