What Is a Serpentine Belt & When to Replace Serpentine Belt?

Serpentine belts are one of those vehicle parts that many motorists hardly pay attention to as they seem to last a lifetime. However, these belts play a crucial role in any vehicle and hence the need to understand what they are all about. A motorist needs to know the advantages of using one in good shape and when to replace what you have.

What is a Serpentine Belt?

The serpentine belt or accessory belt is the main belt on your engine that you see when the vehicle’s hood is open. It has some distinctive ridges running its entire length on one side that make it super easy to identify. These ridges play a crucial role in the belt’s functioning as they ensure it maintains a good grip when moving the accessory pulleys.

A vehicle’s engine has different accessories such as air conditioning, power steering, alternator, and water pump. These accessories get their power from somewhere, and contrary to widespread assumption, it does not come from the batteries.

As the engine runs, the crankshaft spins, and it is this motion that is used to power the accessory pulleys the accessories mentioned above rely on for power. Serpentine belts are what transfers power from the spinning crankshaft to these pulleys. 

For supercharged vehicles, the serpentine belt also transfers power to the supercharger. What’s more, for many cars, the belt helps provide extra electrical power for other functions like charging the battery.

serpentine belt
Photo: Depositphotos

What is the Advantage of Having the Belt Replaced?

The main advantage of replacing a broken or worn-out serpentine belt is to keep the vehicle’s engine running smoothly. When the belt is not in good shape or slips from its track, the functioning of different car accessories like the power steering pump and the alternator is greatly affected.

Besides just failing to work, the parts powered by the serpentine belt can also be damaged if it is faulty, which translates to more expensive vehicle repair. In some worst cases, a defective serpentine belt can start a chain of issues that end up damaging your engine beyond repair.

Therefore, replacing your serpentine belt on time minimizes the risk of the vehicle breaking down and ensures worry-free drives for you.

When to Replace Serpentine Belt

A motorist must understand when to replace the serpentine belt as it has a massive effect on everything from how the car drives to its safety. While your mechanic is always in a better position to tell you when to do it, here are the most common situations when your serpentine belt requires a replacement.

Belt Lasts for Recommended Mileage

A serpentine belt is a rugged vehicle accessory made from high-quality rubber and is guaranteed to last a long time. Hence, most vehicle owners hardly ever see the need for a replacement. However, like any other vehicle part, the manufacturer provides a specific mileage when you need to replace this belt.

Therefore, whether the belt is damaged, worn out, or still looks excellent, it is vital to replace it when it attains the manufacturer recommended mileage. For most vehicle types and models, the manufacturer recommends changing the serpentine every 50,000 to 100,000 miles as that is how long a typical one lasts.

Cracks and Clear Wear/Damage on the Belt

When you notice your serpentine belt has cracks, signs of damage, or even excessive wear, it is time to get a new one. The physical signs can also include a huge chunk of the belt missing and rib separation.

Given how easy it is to access the serpentine belt, motorists should not have any difficulties inspecting its condition as they only need to open the hood and look at it. Making it a habit to check the belt regularly when servicing the vehicle ensure you replace it in good time.

Squealing/Chirping Noise

A damaged or faulty serpentine belt often starts slipping from its track, which manifests in the form of squealing and chirping noises. This loud and annoying sound comes from the front area of the vehicle, and in most cases, you can even hear it when sitting inside the car. 

The squealing sound also often indicates serpentine belt issues like belt stretch or low belt tension. While sometimes a proper tensioning and realignment of the belt can be enough to fix this problem, in some cases, the belt is damaged, and the only solution is a replacement.

Air Conditioner Stops Working 

While various things can lead to a malfunctioning air conditioner, a bad serpentine belt is often the source of the problem in many instances. 

The belt delivers power from the crankshaft to the air conditioner system, and so if it is faulty, the unit does not get the required power. Hence if you switch on the air conditioner and it does not work or seems to misbehave, a bad serpentine belt is among the possible sources of the problem. 

Engine Overheating

Since the serpentine belt powers the water pump pulley, a bad one means it will not work correctly or even fails to work entirely. A damaged or worn belt does not activate the water pump, meaning the engine will not be cooled down, which then causes it to overheat.

When you notice your engine temperature moving towards the red zone, you have to check the serpentine belt soonest to avoid permanent engine damage.


CarCareTotal showcases some excellent quality models for different vehicle types and models if the time has come to replace your serpentine belt. Their top overall recommendation is the Bando USA 6PK1305 which adheres to OEM specifications and features strong tensile cords that carry higher horsepower without ever stretching. Additionally, this serpentine belt has ground rubber ribs, is heat-resistant, and offers broad vehicle compatibility.


The serpentine belt plays a crucial role in a car’s engine. It transfers power to essential accessories like the water pump, alternator, and air conditioner to keep them running smoothly. While these belts are designed to last a long time, it is crucial to know when to replace them by watching out for signs like the accessories failing to work correctly. When it is time to replace one, remember to get an OEM-quality replacement for the best service.