A car making humming noise at 40 mph can be linked to many problems, such as a bad wheel bearing or worn tires. Sometimes only adding or changing the engine oil stops the noise, but other times worn parts need replacement.
This complete guide explains everything that can go wrong to produce a humming or buzzing noise, as well as how to fix the issue.
Contents
Why Does Your Car Make a Humming Noise at 40 Mph?
Your car makes a humming noise at 40 mph because of unsuitable or worn tires or low engine oil or transmission fluid levels. A cracked serpentine belt fails to drive different accessories and produces the same noise. Moreover, the failure of a mechanical joint can also be noisy.
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Damaged or Unsuitable Tires
You might have unbalanced tires if your car makes humming noise at 30mph or 40mph. It is a common reason for such noises, and luckily, it is easy to fix. Tire imbalance means that the weight distribution is unequal for the tire surface.
Equal mass distribution on the tires ensures a smooth drive without vibrations. The car may lose this balance if you drive on uneven paths or if it has poorly constructed tires.
Such tires hum when you drive, and you may notice the humming noise in car getting louder with speed.
Apart from the noise, you will also experience the following:
- Steering pulled to one side
- Uneven damage to the tires
- High pressure on the suspension
- Vibrations in the steering wheel, seats, and floor
You should always keep a check on the tires to detect uneven damage. Scalloping or tire cupping is a common problem. These issues cause vibrations in the car, which can be misunderstood as a humming sound.
The only way to detect it is by visually examining the tires. Having over or underinflated tires can lead to poor or uneven tread depth. Moreover, off-road drives can also accelerate the wearing.
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Humming Due to Low Engine Oil
Low engine oil can also cause a loud humming noise at 45 mph or higher speeds. The oil reduces friction in the engine parts by lubricating all moving elements. Loss of lubrication can damage these parts because of heat dissipation, so the car makes humming noise at certain speeds.
Your car engine has many metallic components that have mechanical functions. When these components move and come in contact with other metallic surfaces, the car makes a buzzing noise. The oil prevents this noise, but if your car does not have enough of it, there will be friction between the parts.
The engine also has different bearings for smooth mechanical operations. These bearings need a continuous oil supply; otherwise, they may jam or wear out. Moreover, when the oil depletes, the engine has to put more effort into running the car components. Therefore, when it works harder, it produces a humming or buzzing noise.
You can check the oil level yourself by following the steps below:
- Park your car on a flat or even surface and wait for the engine to cool.
- Use your car’s user manual to find the dipstick. In some automobiles, it is on the side of the engine, while in others, it is on the front. The stick usually has an orange or yellow handle.
- Pull it out of the tube, wipe off the oil using a cloth, and put the stick back in the tube.
- Pull out the stick and notice the oil level by comparing it to the marks. The marks will show if the oil level is low or full.
While you are monitoring the oil level, you should also inspect the oil quality. Notice the color and smell. The clear or light brown color is fine, but very dark oil is a sign that you need to change it.
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Humming Sound From Worn Wheel Bearings
Wheel bearings are important components of a vehicle’s wheel assembly as they allow the wheels to revolve smoothly. They connect the axle or spindle to the revolving wheel hub through a low-friction interface. Thus, a car making whirring noise when driving might have old or bad wheel bearings.
The bearings distribute the car’s weight and the forces exerted on the wheel between its inner and outer rings by the rolling components. Any damage to the bearings causes prominent discomfort while driving.
You will hear the inconsistent wheel bearing noise, especially when you speed up. The car will also vibrate, and you will feel it through the floorboard and steering wheel.
Another sign of worn wheel bearings is the change of noise with the load. You will hear different noises as you change the load in the car.
Detecting this problem is easy because the symptoms appear as soon as the bearings start to get damage. Also, notice your car’s precision because the steering feels loose when there is a problem with the bearings.
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Noise From Cracked Serpentine Belt
A vehicle making noise at 40-50 mph can be linked to a cracked serpentine belt. It is a long belt that transfers power from the crankshaft to other mechanical components. The belt transfers the rotational power to run different car accessories. These include the alternator, water pump, air pump, tensioner, compressor, and other parts. The belt keeps all functions synchronized for efficient car operations.
After a certain period, the belt starts to age. It is also exposed to heat and pressure throughout its life, which dries it up. As a result, the belt starts to crack. Moreover, the belt slips due to friction and produces noise. The sound comes from the accessories attached to the belt because it fails to drive them.
Right after you suspect a tearing serpentine belt, you should replace it. Replacement is necessary because a torn belt only produces noise, but if you keep using it, the pulley will eventually snap off. If prolonged, the whole system can fail, leaving the pumps, air conditioner, and other parts inoperable.
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Humming Due to Transmission System Issues
Your car’s transmission is basically a gearbox that transmits enough power to the wheels so they can run at your desired speed. Since it holds great importance in your car’s operations, you should never ignore a problem with the transmission.
Transmission has many parts, so if any of them wears out, the car produces noise. It also explains the Nissan Altima humming noise when accelerating. For instance, the bearings inside the transmission components can wear out and produce noise. The noise will get louder as you speed up because it puts the transmission under higher stress.
Similarly, a problem with the torque converter or transmission pump produces whining or buzzing noises. Provided that your car has a manual transmission, you might hear buzzing noises while changing gears. It happens when the synchronizer ring wears out.
However, the most common problem is the lack of transmission fluid. The fluid works as a lubricant to cut friction between different parts, but low fluid levels lead to noises.
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A Defect in the Car’s Mechanical Joints
A car making humming noise at 50 mph can be due to a defect in the mechanical joints such as U-joints, ball joints, or CV joints. Although these joints have different jobs, they produce a buzzing noise when they fail.
The most common cause of car joint failure is a lack of lubrication. Since these parts move, low lubricant increases friction and heat, which damages the joints.
Other reasons for failure include:
- Corrosion due to contaminants such as dirt or debris
- Putting excess weight in the car or towing
- Improper installation or misalignment
- Distortion due to car accident
The noise from worn ball joints is low-pitched, and apart from the failure reasons said above, gearbox or clutch problems can also be damaging.
If you hear the noise and your car fails to accelerate, you might have bad CV joints. These joints are present close to the wheels and are covered by a boot. The boot might wear out the joint, exposing the joint to road dirt.
How To Fix a Car That Makes a Humming Noise at 40 Mph?
You can fix a car that makes a humming noise at 40 mph by balancing uneven tires or replacing the tires with worn tread. Filling or changing engine oil or transmission fluid may stop the noise. Otherwise, you can buy new wheel bearings and get them replaced.
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Balance or Replace Uneven Tires
You can balance the tires in your garage with or without a balancer. Having a balancer makes the process easier and faster, so it is better to invest in a wheel balancer. All you have to do is remove weights from the wheels, lift the car with a jack, and remove the wheels. Since the wheels are off, you can clean the tires by washing them or using a brush. Then you can set the wheel assembly on the wheel balancer.
The balancer comes with a manual, so you can follow the steps. Always remember to mark the spots where you will put the weights. You can recheck the balance after placing the weights to adjust if needed.
If you do not have a balancer, you can adjust the weights by following these steps:
- Identify the problematic wheel and remove its weight.
- Make sure the tire is clean, if not, try to clean it without removing the wheel.
- Place the weight on one side, say in the 12 o’clock position, and rev the engine until the car vibrates.
- Increase the speed by 5 or 10 mph and slightly move the weight from its position.
- Again, speed up, and if you still notice vibrations, move the weights.
- Continue this until the car stops vibrating and you find the perfect tire balance.
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Fill Engine Oil or Transmission Fluid
If your car makes noises because of a lack of engine or transmission lubrication, it can severely damage the car. You should check on the lubricant levels to avoid problems that are more expensive to repair. The oil or transmission fluid does not cost much itself, but the labor cost can be high.
You can save $100 to $150 by changing it yourself. If the fluid is dark in color, pump it out by using a vacuum. Then you can refill the pan or oil reservoir with transmission fluid or engine oil, respectively. Lastly, drive the car for a while to see if the noise goes away.
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Replace the Bad Wheel Bearing With a New One
Replacement of a wheel bearing can be expensive. The bearing is costly, and only an experienced person can replace it, so the labor cost is also high. You can expect to spend a total of $100 to $600. This cost range includes labor, a new wheel bearing, and extra components.
Always buy the wheel bearing from a reputable brand to prevent premature damage. You should also consult the car’s manual to get a suitable bearing for your car.
Conclusion
This article has given you a precise understanding of what to expect from a car that is making a humming noise at 40 mph.
Here are a few points to take along:
- A bad wheel bearing and uneven tire wear are the most common reasons for the humming noise.
- Poor engine and transmission lubrication, worn serpentine belts, or worn joints also produce noise.
- Replacing the bad wheel bearing or the uneven tires or filling lubricants can stop the noise.
Although the noise might not be annoying in the beginning, you should never avoid an inspection. The noise usually indicates a serious problem that may damage the car if left unchecked.
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