Cars made today are pretty quiet. Even one that is working well and firing on all cylinders, so to speak, barely makes a whisper. This can make it particularly jarring when you hear your car making some unexpected sound — either under the hood or underneath the vehicle. It helps to know what the sounds you hear mean. These sounds are essentially the car trying to tell you something important. Knowing when it is time to bring your car into for repairs often starts with an unexpected and unfamiliar sound. To help decipher those noises, here is a list of sounds cars make and what those sounds mean.

A Knocking in the Engine

Before you panic when hearing this sound, keep in mind that a knocking in the engine is usually caused by using the wrong type of gasoline in the car. Filling up your vehicle with a low grade gasoline when it requires higher quality octane causes havoc with the spark plugs, which leads to the pistons moving erratically. This can cause the knock knock sound that you hear. Consult the vehicle owner manual and ensure that you are using the proper type of gas. Once you fill the tank with the right gas, the knocking sound should quickly disappear. No need to bring the vehicle into a garage for a costly inspection, and no need to worry. A little knowledge goes a long way.

Clicking Sound Under the Hood

If you hear a soft clicking sound beneath the hood of your car, fear not. The most likely issue is that the vehicle is simply low on engine oil. The next time you stop for gas, be sure to check the oil level. If it is low or empty, add some oil. The clicking noise should be gone. However, if the oil level is fine, then the issue could be a loss of oil pressure somewhere in the system. Or your car could be experiencing a blockage that is preventing the oil from circulating properly. This is most often due to a build-up of crud in the car. If it’s not an oil issue at all, then the clicking sound is most likely due to a faulty valve train, which may need adjusting. Here’s hoping you’re just low on engine oil.

A Roaring Sound That Increases With Acceleration

Does your car sound like the engine is revving too high when you put your foot on the gas pedal? Do you hear a roaring sound when it accelerates to higher speeds? Does it sound like an airplane taking off? If yes, there are a couple likely problems with the car.

First, there could be a problem with the vehicle’s exhaust system. That can cause the engine to work extra hard. Second, there could be issues with the transmission. Hope and pray that this is not the case, as transmission problems are expensive to fix. If the car in question has an automatic transmission, there could be a problem with the car switching gears. The gear exchange could be slipping, as mechanics say. In a manual transmission, the clutch could be slipping. Whether it is the exhaust or the transmission, it will likely cost time and money to both diagnose the issue and repair it.

A Flapping Noise

Do you hear a flapping sound? Almost as if you’re driving on a flat tire, only all the tires on the car are fully inflated? If yes, then it is most likely that you have a broken fan belt in the engine of the car. The good news is that replacing a fan belt is a pretty standard and easy fix. It is also relatively inexpensive.

However, if you ignore that flapping sound and continue to drive for an extended period of time, it could lead to more serious problems under the hood. And more expensive repairs. That’s because the fan belt helps to keep the engine cool while driving. Specifically, it uses the power of the engine to run the water pump, which cools the engine. Continuing to operate the vehicle with a broken or unreliable fan belt can lead to the engine overheating. An overcooked engine can quickly turn into scrap metal. Pay attention to that flapping sound and act quickly to get the fan belt fixed.

Whirring Sound Beneath the Car

Noises from underneath a car are tricky. Pinpointing the exact cause of the noise can be extremely difficult. However, if you hear a whirring sound under your car and you find that the vehicle is pulling to one side, chances are that a wheel bearing is shot in one or more of the tires. Other possible causes of a whirring sound could include a need for additional lubrication, the transmission may be on the fritz, or the universal joints may be wearing down.

Regardless, you’ll want to get this sound investigated by a trustworthy mechanic as soon as possible. Since noise from beneath your car tends to reverberate and echo throughout the whole vehicle, it can be extremely difficult to identify the exact source of the sound.


If you hear an extremely loud bang when you start your car, similar to a shot gun blast or the sound of a cherry bomb exploding, it is called a backfire. It’s usually accompanied by a large cloud of black smoke coming from the tailpipe. This is almost always indicative of a problem with the catalytic converter, which helps ensure that the emissions coming from your car’s tailpipe are not too harmful. (Spoiler alert: they are still harmful.)

This sound is a rough one, as the catalytic converter is expensive to replace. The fix is typically about $2,500. If the catalytic converter shuts down completely, then your car will not start at all. So getting this looked at by a mechanic is required. Your startled neighbors will thank you.

Hissing Under the Hood

That hissing sound you hear when you first pull into your driveway and shut off the car does not mean there is a snake nearby. It means that something is leaking in the engine. The hissing is the liquid in question falling on hot engine parts. Leaking substances could include coolant, oil, or transmission fluid.

Alternatively, the hissing sound could just mean that the engine is overheating. Regardless, if you hear a hissing noise under the hood, get out of your car and look underneath it. Chances are you will see a black, red, or fluorescent green liquid pooling on the driveway or the garage floor. Get this fixed immediately at a qualified garage. Leaving it will only cause bigger problems for your car. And make a mess of your driveway or garage.

Popping Noise in the Engine

While there can be lots of reasons for a popping noise in the engine, it’s usually due to faulty spark plugs. If the popping noise is followed by the engine hesitating or the car jerking, then chances are it’s the result of worn, dirty, or damaged spark plugs. A bigger problem could be an issue with the car’s ignition. But start by assuming it is the spark plugs.

The good news is that spark plugs are inexpensive to buy and can usually be replaced yourself, rather than an expensive mechanic. Go to a local automotive store and buy some spark plugs. If the popping noise is gone after you install them, then you know the problem was caught and fixed. If the popping persists, see a mechanic. Don’t worry about spending time and money replacing the spark plugs, if the noise didn’t stop. It’s a good idea to replace those periodically anyway.

Rattling Beneath the Car

While many sounds from underneath a car can be difficult to source, there’s no mistaking a persistent rattling from under the driver’s seat. This almost always means that there is something loose beneath the vehicle. It’s usually the exhaust pipe. The good news is that it’s usually pretty easy to spot what is loose, as the item is typically hanging down in plain sight.

In most cases, you can tighten a loose exhaust pipe yourself with a screwdriver, or secure it using some tape. Just be sure to address this problem before your exhaust pipe is scraping along the ground or falls off the car altogether, resulting in a costly repair. If you see something hanging down beneath your car that you can’t identify, be sure to see a mechanic.

Screeching When Applying the Brakes

Last, but certainly not least, we come to the sound of screeching brakes. Nothing quite says your brake pads are worn out like the screeching sound you hear when pressing your foot down on the brake pedal. Sometimes your brakes will screech a bit when a car’s tires are wet, but this usually goes away once the water evaporates.

However, if the screeching persists, it’s a sure sign that the brake pads are worn down. They probably need to be replaced. If you hear a grinding noise accompanying the screeching, we have bad news for you. That’s the sound of metal scraping against metal, meaning the brake calipers (and possibly rotors) are now an issue too. They should be replaced or repaired.

Regardless of the extent of the damage, brakes should always be kept in good working order. If there is one thing you do not want to mess with, it’s the brakes on your car. Keep them working properly and keep yourself safe in the process.


This article was worked on by a variety of people from the Autoversed team, including freelancers, editors, and/or other full-time employees.