Car Noises ~ How to Diagnose Them

Car noises are something you should pay attention to.  Diagnosing where a noise in your car is coming from can be a daunting task at times.  I wrote an article for my shop website about why you don’t want to ignore noises that you hear.  You can find it at:

So That’s What That Noise Was…

Let’s take a look at ways to identify noises heard on your car.   The method will vary depending on what area of the car the noise is coming from.  You can also narrow the search by identifying characteristics of the noise.   Understand that these are guidelines, and as with all things in the world of car repairs, anything is possible.

Speed Related

Is the noise related to the speed the car is moving?  Do you hear the noise when the car is in gear, in park or neutral, or both?   If it is speed related, it is likely in the drivetrain or wheel bearings.  Drivetrain consists of transmission, drivelines, axles, differentials and transfer case if all wheel or four wheel drive.  Wheel bearings are at each wheel, or axle depending on the type of suspension.  A wheel bearing will typically produce a humming sound that is speed related.

Engine RPM Related

Noises that change with engine speed are going to be found under the hood.   Engine noises can change just by RPM, this classification of noise must be isolated from engine load sounds.   RPM related noises will probably be in the drive belt area, belt-driven accessories, timing components, or water pump.  Some internal engine components such as valvetrain components can also be RPM related.

Engine Load Related

Engine load is created when you are accelerating the vehicle, or putting it under a load.  You can simulate in a car with an automatic transmission by applying throttle while stepping on the brake.   Although some on some of the newer models, the on board computer will not allow you to do that.  When you hear a noise that changes when the vehicle is under a load, generally it will be either an exhaust noise, or an internal engine problem.  Other things to consider are bad motor mounts as the engine can move around or be in contact with the frame of the car.  Also exhaust system can move and hit the body or frame of the car.

Tools to Listen With

While it is possible to detect the origin of some sounds or noises without tools.  For example, you can sometimes tell which wheel bearing is making noise by steering the car to one side or the other while driving a straight line.  The bad wheel bearing will generally be louder when more wight or load is put on it.  However, it can be much easier with a small investment. I have a few tools that I use in my shop to pinpoint the sounds.


The most basic to is a stethoscope.  There are many different brand so stethoscopes, and really the all do the same thing.   Lisle is a good choice for the home mechanic  and OTC tools are always very good quality.

A stethoscope is generally used just like the one your doctor uses, except it has a probe to touch around various areas of the engine to isolate a noise.  You can also remove the probe and use the open tube to find a general area it it is a noise like a vacuum leak.  The open tube also works very well for pinpointing air noises around a windshield or door.

Electronic Listening Tools

Steelman makes some very good electronic noise detection tools. The engineEar works much like a stethoscope but is much more precise.  They also make a chassisEar, available in two  versions.  Both versions do the same thing, however one is much more user friendly.
 The wired version has leads that you can attach to up to six chassis components or drivetrain components.  You route the leads to a control box where you control which lead you are listening to with a 6 position switch.  The sound is then amplified and sent to the headphones.  As you drive the vehicle you can switch to the different components that you have attached the leads to and isolate where the noise originates.  This works particularly well when determining which wheel bearing is making noise.  The other vesion of the ChassisEar is wireless.
The wireless version of the ChassisEar is much easier and faster to set up.  While it is limited to 4 leads vs the 6 leads on the wired version, the ease of setup makes this model a clear winner for professional use.  Either system is a great way to isolate noises while driving.

Do Not Ignore It

You can you choose to find the source of car noises on your own, or have a professional diagnose it.  The most important thing is to not ignore it.  If your car is making a noise, you need to at least know what it is so you can determine if it is doing more damage  or is a safety concern.  Some noises are just annoying and really are of no great concern, while others can be doing costly damage to your vehicle.  In worst case scenarios, the cause of the noise could be dangerous and a concern for the safety of yourself and others.  Listen to what your car is trying to tell you.





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