Knocking Noise When Driving – What’s The Cause?


There are few things in life more irritating than a continuous knocking noise when you are driving your car. The constant tapping and banging can drive you insane. However, few people actually know the root cause of that annoying knocking sound or how they can stop it. 

A knocking noise when driving happens when there is an issue with the vehicle. Some knocking noises can indicate dangerous problems with the car, and other knocking sounds indicate minor issues. Banging noises can signify anything from suspension damages to engine mechanical issues. 

Keep reading for an in-depth analysis on why cars and other vehicles make a knocking noise when driving. I will look at the most likely causes of these sounds and what you can do to stop them. 

What Are the Most Likely Causes of a Knocking Noise When Driving?

If you want to free yourself from that annoying knocking noise when driving, you first must figure out where the sound is coming from. It’s not always straightforward figuring out the root of a knocking noise. 

Here are the most likely causes of a knocking noise when driving: 

  • Detonation knock 
  • Suspension damaged 
  • Bad belt tensioners
  • Worn out steering rack 
  • Damaged axle shaft 
  • Worm bearings 
  • Dirt or ice build-up 

See below as I break down each of the points mentioned above to help you figure out why your car is making a knocking noise. 

Uncontrolled Detonation in the Engine 

A detonation knock is a likely cause of knocking sounds when driving. It happens when air and fuel mixtures within your vehicle’s engine combust unexpectedly. These unexpected miniature explosions collide and make a knocking noise that drivers can hear. 

A couple of issues can cause a detonation knock, such as: 

  • There may be issues with the fuel you are using if you drive a performance-tuned vehicle. 
  • When engines are out of sync or have a poor knock sensor. 

Detonation knock sounds similar to popcorn or bacon sizzling on a frying pan or may sound more metallic. It’s not a significant problem if the issue is addressed early. Prolonged driving, however, may worsen the case and cause extensive engine damage. 

Therefore, it’s best to bring your vehicle to a mechanic if you suspect it has a detonation knock. 

Read: Automatic Transmission Have Grinding Noise When Put in Gear. How To Fix?

Worn Out or Damaged Suspension 

Not all knocking noises start in the engine of your car. 

Another likely culprit to knocking sounds is damaged or worn-out suspension. A clear indicator that your knocking noise is coming from the suspension of your vehicle is if it worsens as you go over bumps or eleven ground. 

Suspensions may also cause a knocking sound as you drive at higher speeds, which will be evident because the knocking will become faster as you go more quickly. The suspension of your car is integral in driving comfortably and safely. 

Therefore, it’s best to have any knocking noises from the suspension assessed by a professional. 

Fixing the suspensions on your own is a labor-intensive, expensive and dangerous task. As a result, it’s a job best left to the professionals as a mistake involving a suspension spring could cause severe injury. On top of this, you could cause further damages that need repair. 

Read: Why There Is Noise When Turning Steering Wheel While Stationary?

Belt Tensioners Need Replacing 

The timing belt tensioner is a component on the front of a car engine and runs across a pulley attached to the tensioner. If the timing belt tensioner has become worn, it can trigger a knocking noise in your car as you drive. 

The best tensioner holds the timing belt at the proper tension. If the belt tensioner comes loose or wears down, it will begin knocking against the timing belt. When the strap tensioner makes a clicking or knocking sound, it’s likely gone bad. 

Similarly, the belt tensioner may cause a chirping noise as it grinds against the timing belt. 

A damaged belt tensioner can cause harm to the timing belt in your engine. If the timing belt is severely damaged, it will likely cost hundreds, if not thousands of dollars. Therefore, it’s best to repair your belt tensioner at the first sign of an issue. 

Belt tensioners should be repaired or replaced by experienced professionals. If you make a mistake while attempting to mend a belt tensioner, there’s a strong likelihood of you causing further damage to the vehicle. 

Read: Why Car Makes Noise When Turning at Low Speed?

Steering Rack Is Worn or Damaged 

The steering rack in your car is another likely culprit of a knocking noise as you drive. If the steering rack is vent out of shape or damaged, it will cause a knocking noise that will increase intensity as you accelerate or drive over uneven ground. 

Steering racks become worn out and damaged over time. Therefore it is no cause for primary concern when your steering rack is not working as it should. 

However, the steering may feel loose with a worn-out steering rack. 

Repairing a worn or damaged steering rack is complex and often expensive. As a result, it’s one best left to mechanics as they have the specialized equipment and experience needed to repair or replace the worn or damaged steering rack fully.

Read: Check This If Your Car Is Making Noise When Turning 

Bearings Are Worn Out 

If the bearings are worn out on the wheels, this will trigger a knocking sound as the wheel spins. This knocking sound occurs as the wheel is not spinning freely due to the damaged bearings. 

The sound produced is a loud thumping noise that will increase intensity as the wheels spin faster. 

Bearings wear out in wheels over time due to normal wear and tear or the car wheels being out of alignment. On top of this, constantly driving over rough terrain may cause bearings to seize up or wear down. 

When the wheel bearings are worn out in a car, there is little that you can do to repair them. It’s usually more cost-effective to replace the whole wheel with a new one. This is a relatively simple repair that you can carry out at home. 

However, you will need to find a new wheel before replacing the existing one. 

Dirt or Ice Collecting in the Engine or Near Wheels  

Another common source of loud knocking noises while you drive is a build-up of dirt and ice underneath the vehicle. It can form and accumulate in spaces beneath the car. Then as the car travels, this build-up may scrape against the floor underneath, causing scratching or knocking sounds. 

Dirt and ice can also accumulate near the wheels of the vehicle. As the wheels start turning, they grind and bang against the build-up, which leads to a continuous knocking sound whenever the car is in motion. 

These knocking noises may reduce after driving for a few minutes as the build-up has worn away. 

To stop dirt and ice from building up on the underside of your car, you must check underneath and around wheel arches before driving. If you come across a build-up of mud or ice, use a cleaning utensil or garden hose to dislodge the build-up. 

This will free the mass from beneath the vehicle and prevent it from knocking against the wheels while driving, which should prevent the knocking noise from returning while you are driving. 

Another good way to clear snow and other debris from under your vehicle is to take a pre-trip inspection and kick it off. If it doesn’t come off immediately, you’ll need to use a crowbar or something similar.

Read: What Are Bad Control Arm Symptoms

Final Thoughts 

There are many more sources of that knocking noise that you hear while driving your car. However, some culprits are more likely than others. 

Here are the most likely causes of a knocking noise when driving: 

  • Detonation knock 
  • Wear and tear 
  • Damages to wheels and suspension
  • Build up of mud or ice 

If you have resolved and repaired all of these potential issues, you may need to bring your car to a garage for inspection. A mechanic will likely find the root of your knocking noise.

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