It always starts off innocently enough. 

You’re driving, and you hear it — that noise. And as much as you try to ignore it, the sound persists. And it keeps getting worse. 

Eventually, it’s time to admit it: “There’s something squeaking in my car’s engine.” Or maybe it’s clunking. Or rattling. Or knocking. Or even thumping. 

Unwanted noises coming from under the hood anywhere on a vehicle are bound to happen — and they always start at the worst time. 

Having an understanding of what these noises are and what they mean help you better prepare for a talk with your mechanic about the issue.

6 Common Auto Noises and What They Mean

While noises coming from a vehicle can have any number of causes, here are the six most common and what problems they likely indicate: 

1. Squeaking
2. Hissing
3. Thumping/knocking
4. Clunking
5. Rattling
6. Screeching 

1. Squeaking 

A question no one likes asking: Why is my car squeaking?

Unfortunately, there are many possible answers. Your first step is to figure out the source of the squeaking. 

If the noise is coming from under the hood when you rev the engine, chances are there’s a loose cambelt. Or it could be an alternator starting to malfunction. 

Squeaking noises from the engine are more common when you turn a cold vehicle on in the winter. As the engine heats, squeaking should subside as its components warm up. 

Squeaking noises from outside the engine compartment indicate issues with your vehicle’s:

• Power steering system
• Ball joints
• Brakes
• Tires 

2. Hissing 

A hissing sound while driving indicates your engine may have a leak in its vacuum system or hole in a hose. If this is the case, you’ll also notice the engine has to work harder to accelerate and a loss in overall horsepower. 

If the hissing persists after you’ve turned off your car, the culprit is likely a component of your radiator. Before doing anything, let the engine cool down for a while. If you’re not careful, you can get seriously burnt. 

A first step to inspecting the cooling system is to check your dashboard’s temperature gauge. If it’s in the red, the hissing is definitely related to the cooling system. 

When the engine has cooled down enough, visually inspect the radiator and any lines connected to it for holes. If there’s a sweet smell coming from the engine compartment, antifreeze fluid has leaked out. Be sure to check underneath your parked vehicle for any puddles of leaked coolant, too. 

3. Thumping/Knocking 

The simplest answer is someone put the wrong fuel in your vehicle. 

Engines are designed for specific fuel types. Using a low-octane gasoline when your vehicle requires premium makes your internal combustion engine act erratically. This causes spark plugs to have trouble doing their job, leading to pistons shaking and banging. 

Other possibilities for that thumping you’re hearing include:

• Worn bearings
• Loose belts
• Items in your trunk rolling around

4. Clunking

This sound is common in vehicles with all-wheel drive and its source comes from underneath

What is it?

Chances are it’s a drivetrain clunking noise, and it likely means you have an issue with your vehicle’s U-joint. 

On all-wheel drive vehicles, the U-joint is what engages all four tires to push your car forward. 

U-joints on vehicles made in the early 2010s need routine lubrication or else the part wears out. Once that happens, anytime your car kicks into four-wheel, you’ll hear a very loud clunking noise. Your car will shake more as you accelerate, too. Depending on your vehicle, the repair may be as simple as replacing the U-joint or as complicated (and expensive) as replacing the entire driveshaft.

While your vehicle is still operable with a failing U-joint, you shouldn’t engage all wheel drive. This is particularly concerning for those driving in the winter or during an intense rainstorm, when your vehicle is most likely automatically to engage all-wheel drive. 

5. Rattling 

It’s hard to ignore a vehicle rattling — especially when the sound is right beneath you. 

Rattling noises under the driver’s side of the car are most likely from a loose exhaust pipe. In the world of auto noise diagnostics, the odds are that an unsecured exhaust pipe is the source. Simply look under your car — you’ll see a low-hanging pipe pretty quickly. 

While you can drive around with a loose exhaust pipe, you’ll be on borrowed time. Eventually, the pipe will lower enough that it makes contact with the ground. 

That rattling noise you’ve been living with — it’ll become a pronounced scraping noise as the pipe’s metal drags against asphalt. 

6. Screeching 

This is one you’ll want to get checked out right away. 

Nothing signals worn-out brake pads like a high-pitched screech as soon as you apply pressure to the brakes. Nearby motorists who can also hear that ear-piercing sound will agree. 

Failing brakes pads aren’t something to drive around with too long. 

Not only do you risk their outright failure and your safety, but also creating a bigger — and more expensive problem. When brake pads are completely shot, you’ll likely start hearing metal grinding every time you slow down or stop. That new sound is damaged brake calipers, and you’ll have to replace those, too. 

You’ve Diagnosed the Auto Noise. Now What?

Unwanted car sounds don’t discriminate against vehicles. No matter how new or how well-cared for, a car is vulnerable to any number of issues — and you’ll likely hear them. 

So what is your next step when you start hearing one of those noises coming from your car? 

The short answer: A trip to your mechanic is in order. 

And no, ignoring the noise won’t make it go away. In fact, continuing to drive your vehicle when it’s making sounds it’s not supposed to usually makes the problem a lot worse and more expensive. 

Regardless of the noise, a DriveSmart Warranty helps you avoid repair bills of any amount. 

Explore this, and other benefits — such as the freedom to choose your own mechanic with no up-front repair payments — our warranties provide.