Auto Noises: My Car is Making a Humming Sound

Why is My Car Making a Humming Sound? 

A humming noise can be caused by a number of different systems in your vehicle. The first thing to assess is where the noise is coming from. A noise you hear at idle and a noise you hear only while driving are two very different problems. A humming sound heard at idle has to be something that moves even while the car doesn’t. This could be a drive belt or one of the components driven by the drive belt, such as the power steering pump, air conditioning compressor, water pump, or one of the idlers that hold the belt in place. Air escaping through a leak can also cause a distinct “humming” noise. This could be a small leak in the exhaust system or air intake system. Sometimes driving accentuates noises that are heard while idling.

If the noise is only present while driving it is likely related to the drivetrain. The drivetrain includes the transmission, drive axles, carrier bearings, and wheel bearings. These components all move or spin while you’re driving. Wear in these components will cause a humming noise as they’re moving.

When these parts wear they will make noise. This wear may not be a cause for immediate concern, but any excessive wear is cause for concern. The worst case scenario for most parts is that too much wear will cause the part to fail. This could mean the car will no longer drive. Or, you may lose some functionality such as the power steering if the power steering pump fails, or air conditioning if the compressor fails.  

What Other Noises or Signs are Related to the Humming Noise while Driving?

• The biggest thing to look out for that would point to a specific issue would be when the noise occurs. You may notice the noise only happens at idle or only happens at highway speed. The noise may also change depending on how fast you’re driving or how much you’re turning the steering wheel.
• Noises that are related to the drive belt will often get louder with higher RPMs but are not affected by vehicle speed. The may change when you’re turning the wheel, such as when you’re parking.
• Noises that are only audible at highway speeds may change when you’re switching lanes or making a long, sweeping turn. Determining when the noise is at its worst helps pinpoint which side the failing wheel bearing or other drivetrain component is on.

How to Fix You Car’s Humming Noise

The first step to fixing the problem is identifying what’s causing the humming noise. The first step we take in identifying the noise is to take the car for a test drive. This usually gives the technician an idea of where to look. Next, we’ll bring the car into the shop and elevate the entire car. We keep the car running and use a stethoscope, similar to what a doctor uses, to pinpoint the location of the noise. We always let you know what the repair costs will be before proceeding with the repair. Often times we’ll need to order parts before performing the repair. We always perform a final test drive after the work is completed to be sure the problem is resolved.

None of these components fail due to any fault of the driver. They’re generally normal wear items that will wear as the car ages. Depending on the car, they may not require attention for more than 100,000 miles. The one good thing to always stay on top of is normal scheduled maintenance. For components like the power steering system and transmission, clean fluid can go a long ways towards ensuring these components last for the life of the car, if not longer!