Humming car noises explained

Common causes of humming noises while driving

If you notice the humming noise particularly when you’re driving, it’s likely to be down to problems with your drivetrain. One of the most common causes is worn-out wheel bearings.

You can test this by accelerating then coasting – if the humming gets louder as you get faster then continues when you take your foot off the pedal, that’s a sure sign that your bearings are bust. (It’s worth noting that if the humming does stop when you coast, you may be dealing with an engine problem.)

Certain drivetrain-related issues only cause humming sounds when you speed up, such as:

• Low differential or transmission fluid levels.
• A failing torque converter.
• A loose or damaged driveshaft.
• Worn transmission gears.
• A worn-out serpentine belt.
• A misaligned steering wheel.

If one of these issues is to blame, you’ll probably hear the humming noise more when you apply throttle pressure, accelerate, or decelerate - or when your car is under load.

If you’re having trouble pinpointing the cause of the humming noises, ask a qualified mechanic to diagnose the problem.

• Humming noises at idle

  A humming noise that you can hear even when your car is idle must be coming from one of the parts that move when your car doesn’t. There are only a few potential culprits in this case: the drive belt, power steering pump, and air conditioning compressor, which does make it easier to spot the issue.

  Your air conditioning compressor will hum if it’s damaged or has a refrigerant leak, as will the power steering pump if it’s faulty or has low fluid levels.

  The drive belt will keep turning even when your car is stationary. So, if it’s loose or worn, you could hear it humming. It’s worth checking your exhaust too, as a leak there might also cause a humming sound.

  If you do hear humming noises when your car isn’t moving, it’s important not to dismiss them, as they could be a sign that these parts are wearing out and need replacing before they lead to further damage.

• Humming noises when turning

  If you hear the humming noise when you’re turning rather than accelerating, coasting, or idling, those usual suspects - worn-out wheel bearings or a faulty power steering pump – could be to blame again.

  Turning puts extra strain on your wheel bearings – and, if they’re on their last legs, they’ll find it hard to take; the humming is the sound of their struggle. Paying attention to whether the noise gets worse when you turn in a particular direction can help you identify exactly where the problem is.

  If the humming is more noticeable when you turn the steering wheel, it could be due to a damaged or leaking power steering pump.

  Don’t ignore these humming noises – they’re your car’s way of telling you that something’s wrong with your steering.

  Remember, if your steering isn’t working properly, you don’t have full control over your car’s handling, which poses a huge safety risk. Therefore, if your car has faulty steering, you shouldn’t attempt to drive it. Instead, arrange for your car to be towed to a local garage for repairs.

• Tyre and road issues leading to humming noises

  If you’ve ruled out all the potential problems covered above, then the humming could be coming from your tyres or wheels, especially if it’s a persistent noise.

  Worn-out tyres, low (or high) tyre pressure, and poor wheel alignment are all possible causes. Low pressure and uneven wear means your tyres aren’t in consistent contact with the road, which can create a droning hum. If it’s more of a vibrating hum you’re hearing, it’s likely that your wheels are misaligned.

  Any of these issues are more than irritating to the ears – they’re also a risk to your safety. To avoid losing control of your car, make sure you regularly inspect your tyres - and get your wheels aligned when necessary.

When to contact a mechanic

If you notice any humming noises, it’s important to get a professional diagnosis, particularly for drivetrain and engine-related issues.

A mechanic will take your car for a test drive so they can hear for themselves where the noise is coming from and when it occurs. They’ll then take the car back to the workshop, raise it up with the engine still running - and use specialist tools to pinpoint the source of the hum.

Once they’ve found and fixed the problem, they’ll take your car for a final test drive to make sure everything’s running quietly and smoothly.

However, keeping up with your regular services can help prevent things from reaching this point. Whilst some everyday wear and tear is inevitable, staying on top of small repairs today can stop them becoming much bigger problems further down the road.

If you’re now dealing with serious mechanical issues, it might be worth considering if you should sell your car rather than shell out a fortune to replace expensive parts.