Cars produce strange noises especially when something is wrong. In most cases, identifying the cause of the noise will be challenging. For instance, I have been hearing a thumping sound from my 2008 GMC Sierra 1500 pickup for the past couple of days, and it gets slightly louder when I accelerate or make a turn.
Here’s what I found after my research.
Usually, a thumping sound from your car is a sign that you have tire problems. When tires are wearing out unevenly, they produce a thumping sound. If the sound is loud enough for you to hear with the windows closed, then it is likely that more than one tire is affected. Sometimes the noise may seem like it’s coming from the tires, but the tires may not have issues.
Since a car has many complex systems, a thumping sound can mean different things.
Here’s a table showing different thump noises, meaning, and their estimated repair cost assuming you have a Honda Civic.
| Car thump noise | Reason or meaning | Estimated repair cost |
| Loud thumping noise when driving | Uneven worn-out tires | $75 – $135 |
| Distinct low thud noise when driving | Steel-belted tires | $75 – $135 |
| Thumping sound from the rear of the car | Uneven worn out back tires | $38 – $68 |
| Sounds like a flat tire | Worn-out struts or shocks | $220 – $897 |
| Thump noise from the front of the car | Broken starter motor mount | $284 – $479 |
| Thumping sound when braking or slowing down | Warped brake rotors | $300 – $700 |
| Thumping sound from the wheels | Worn-out brake pads | $100 – $300 |
| Noise when downshifting | Faulty transmission | $1,700 – $2,700 |
| Thumping (knocking) sound when idle | Worn-out spark plugs | $100 – $160 |
| Thump when driving on a curved road | Bad wheel bearing | $200 – $340 |
| Exhaust thumping noise when the car is at a stop | Damaged exhaust system | $400 – $500 |
| Thud noise on a bumpy ride on a smooth road | Low tire pressure or misaligned wheels | $0 or $140 – $180 |
| Thump (click) sound when turning, a bouncy car | Worn out CV joint | $950 – $1,000 |
The table just gives a snapshot of how to quickly diagnose a thump noise.
Car thumb noises and their meanings
Here’s an in-depth explanation for the different sounds.
1. Noise caused by the type of tires
It would be best to know that different tires make different noises. For example, most tires will make a thumping noise on concrete surfaces with expansion joints.
If you had your tires replaced recently, the problem could be the type of tires. Steel-belted tires are very tough, stiff, and durable but are also very noisy. They have a distinct low thud noise when driving.
Belted tires using fiberglass or synthetic materials are quieter and give a smoother ride.
So if you just got new tires, the thump sound could be from the type of tires you have. But if the noise sounds new and abnormal, that sounds like a problem that needs fixing.
2. Uneven worn-out tires’ noise
If there is a thumping sound from the rear of the car, it is most likely a tire problem.
To put it to the test, try driving your car on a smooth surface with no vehicles at about 2-3 miles per hour and let go of your steering wheel. If the steering wheel is unstable, it means your back tires are wearing out unevenly, which can be dangerous when you start accelerating.
It would be best if you got your wheels replaced immediately.
3. Worn-out struts or shocks
If the car sounds like it has a flat tire but doesn’t, there is a problem with either the struts or shocks.
Your vehicle has struts at the front wheels and shocks on the rear wheels for absorbing shock and support.
When the struts or shocks start to wear out, they vibrate against the car’s body, producing a thumping sound. You will need to replace the worn-out strut or shocks.
4. Broken starter motor mount
Another reason the front of your car is producing a thump when accelerating is a broken starter motor mount.
The starter motor mount connects the engine and the chassis and absorbs vibration coming from the engine.
So if you have a bad starter motor mount and you accelerate, it produces heavier vibrations. Replace the rubber seal on the motor mount to fix the problem.
5. Warped brake rotors
When there is a problem with your car’s braking system, it tends to make a thumping sound when slowing down or braking.
If the brake rotors have worn out or warped, you will hear the rhythmic sound coming from your front wheels, which do most of the braking. You will also feel some vibration from your steering wheel. If they are twisted, you can quickly straighten them without needing a replacement.
6. Noise caused by worn-out brake pads
The pad material on cheap breaking pads wears out quickly and accumulates around the rotor.
Also, the metal chunks exposed by the worn-out pad material can scratch against the rotors and cause a thumping sound.
If you notice your braking pads are worn, you can easily replace them with quality ones.
7. Faulty transmission
A transmission problem can also cause a thumping sound from the front.
To identify this problem, go to a place with no cars and downshift the transmission while allowing the vehicle to slow down without stepping on the brake pedal.
If you still hear the noise from the front of the car, then there is a transmission problem. Check all your fluids and refill them.
8. Worn out spark plugs
Your car could be fine until you’re at a traffic light stop and you start hearing some knocking or thumping sound.
When the engine is not firing correctly on all cylinders, your car will make a thumping sound when idle, which causes heavy vibrations.
If you have worn-out spark plugs, they will prevent the engine from igniting the mixture of fuel and air properly on all cylinders, causing a misfire.
It would be best if you had your mechanic perform a cylinder balance test using a scan tool. A weak cylinder vacuum or thin seal valve may be the reason for a thumping on idle.
9. Bad wheel bearing
The most common way of identifying a bad wheel bearing is a wheel bearing thump when the car is going through a curve that also changes in proportion to the vehicle’s speed.
The noise can also be very inconsistent, and it can be loud sometimes or very quiet on other occasions.
You can confirm the bearings’ condition by jacking the car and rocking the tires back and forth.
Place a dial indicator on the hub while turning the wheel in and out by hand. The dial indicator measures the bearing play. Experts say that any bearing play of more than 0.005 is terrible, and you should replace them immediately.
Identifying the bearing with the problem may be difficult, so you have to measure the wheels bearing on all tires.
10. A damaged exhaust system
A thumping noise coming from your exhaust means there is a problem in your exhaust system. It also tends to be a shallow thumping sound and is more apparent when you stop the car without turning off the engine.
It would be best if you did not ignore any problem signs from your exhaust as it could leak carbon monoxide into your car.
11. Low tire pressure
When your car makes thudding noise while driving, it means that your tires have low and uneven air pressure. It could also mean that your wheels are misaligned. If you do not have a flat tire, the thud noise is usually accompanied by a bumpier ride, especially when driving on smooth roads.
12. Worn-out CV joint
After a trip to the mechanic, my car’s diagnosis is a damaged Constant Velocity joint (CV joint) on the left side, which the mechanic replaced. I also noticed grease dripping along the inside of the wheel rim from a tear in the CV joint.
The CV joint transfers power from the transmission to the wheels at a constant speed while supporting the suspension’s up and down motion. So when it wears out, it makes a thump or a click sound when turning, and the car also becomes bouncy.
Any unusual sounds coming from your car is always an excellent way to identify a problem before it worsens and leads to more expensive repairs. Since people describe sounds differently, you have to take your car to get a more professional diagnosis and repair.
