There was a group of engineers that designed your vehicle that worked on its NVH (Noise, Vibration and Harshness) characteristics. Their goal was making your vehicle pleasing to drive while minimizing noises, vibrations, and how smoothly it would absorb bumps. Of course they had a budget to stay within.
The day you drive a new car off the lot you may start to recognize the limitations that that budget had on your vehicle. Noises begin to develop.
In the dealership service department there will likely be a mechanic that specializes in finding the cause of noise complaints and repairing them. It can be a very challenging job. When a car is new, the tolerance level of any abnormal or perceived abnormal noise is very low. Especially if said vehicle is under warranty.
As vehicles age the owners begin to accept a little noise here and a little noise there, particularly when they know they will have to pay to stop the noise.
In the mechanics’ trade finding the cause and fixing a noise complaint is a regular job. Sometimes I think it can be a lot more difficult working with older vehicles than new vehicles.
Many older vehicles present a cacophony of noises and it is sometimes impossible to determine what noise the customer is concerned with. A mechanic will be listening for a noise that sounds like serious mechanical failure is on it’s way while the owner will be stuck on a little brake squeal that embarrasses him when he drives home through his neighborhood.
I know that many times I have fixed the wrong noise but it was an important noise to fix. Customer satisfaction suffers though in those situations.
A road test with the customer is the best way to get on the same page when it comes to noise solutions. Many times the owner will have to drive the vehicle in the correct manner to reproduce the noise.
Many times the presence of a mechanic automatically quells the noise similar to a trip to the doctor. “Where does it hurt? Nowhere now.”
Do not forget to be very logical about that disappearing noise. Two people being in the car instead of the typical one may be the difference between noise or no noise. The extra weight of an extra passenger can change vehicle dynamics.
Your mechanic will have a small arsenal of noise diagnostic tools. Some will be seemingly archaic (yet indispensable) like a long screwdriver for listening through. He/she will also maybe have a stethoscope (makes me feel like a real doctor). There are now also ultrasonic listening devices for air leaks and multi channel listening devices with electronic pickups to attach to the part suspected of producing the noise. They will typically have headphones for listening to determine which electronic pickup is closest or connected to the source of the noise.
Sometimes the noise must be analyzed for frequency in order to get to the source. Engine noises can be tricky that way. Many shafts and bearings on the engine turn at different speeds. Frequency analysis can help to determine which shaft or bearing is the culprit.
So what if you cannot find the source? Time may tell. The noise could get worse and the source more evident.
Don’t forget the obvious though! Loose wheels, loose wheel covers, low oil levels, and loose items in the trunk are much more common than people think.
Turning up the stereo is not necessarily the best solution.
Trail’s Ron Nutini is a licensed automotive technician and graduate of mechanical engineering from UBC. He will write every other Thursday. E-mail: firstname.lastname@example.org