Q: I own an older vehicle with higher mileage. I recently had new fan belts installed after hearing a high-pitched, whining noise, but that didn’t solve the problem. What else could be causing the noise?
A: There are many potential causes for a noise of this type. To narrow the possible causes, answer the following seven questions and provide your technician with the information.
1. Do you hear the noise when the engine is running and the vehicle not moving?
2. Does the noise change with the engine speed?
3. Is the noise heard only when the vehicle is put in gear?
4. Is the noise heard only when the vehicle is being driven, and does it change with the speed of the vehicle?
5. Is the noise heard only when driving and turning corners?
6. Is the noise heard only when applying the brakes while driving?
7. Is the noise heard mainly when starting the engine and then only occasionally thereafter?
Following are examples of what the answers to these questions could point to.
• It could be that the fan belts were installed but not tightened correctly. Affirmative answers to questions 1 and 7 would point to this being the problem.
• There are bearings in the components being driven by the fan belts. One or more of these could be the source of the noise. Affirmative answers to questions 1 and 2 would point in that direction. These bearings could be in the alternator, water pump, power-steering pump or pulleys that tension and guide the fan belts and timing belt.
• If the noise is not heard until the vehicle is put in gear, either with an automatic or manual transmission (question 3), the cause of the noise could be internal to the transmission (for manual transmissions) or could be a clutch problem.
• An affirmative answer to question 4 – the noise is heard only while driving – could point to the drivetrain. Sources could be the wheel bearings, in the transmission or a differential.
• An affirmative answer to question 5 would direct attention to the drive axles or could indicate a wheel bearing.
• If the noise is only heard when the brakes are applied (question 6), the brakes are the likely source. Possible causes include worn-out brake pads, faulty brake calipers, not enough or no lubrication on the brake parts or simply low-quality brake pads and/or brake rotors.
Special tools are sometimes needed to locate the source of a noise, such as Electronic Ear Sensors. These are clipped to different areas of the vehicle, and each sensor can be listened to individually to help determine the cause.
It is important to be prepared to provide as much information as possible when bringing your vehicle in for service. Note that providing the specific details to your technician is only the beginning step in identifying the cause of the noise. A qualified shop will then take that information and determine where to begin diagnosis, saving a lot of time and thus money in the long run.