Serpentine Belt Guide (Function, Benefits, FAQs)

The serpentine belt is one of the most important components in your car.

But it’s also one of the least talked-about parts.

So what is a serpentine belt?
Is it the same as other engine belts?

In this article, we’ll explore the twists and turns of the serpentine belt and the benefits of having it in your car. We’ll then go through some FAQs to better understand this simple but crucial vehicle component.

This Article Contains

What Is A Serpentine Belt?
What Does The Serpentine Belt Do?
What Are The Benefits Of The Serpentine Belt?
7 Serpentine Belt FAQs

Let’s begin.

What Is A Serpentine Belt?

As its name suggests, the serpentine belt is a long, winding rubber belt that loops around spinning engine components. It’s typically made of high-quality reinforced rubber and has multiple V-shaped grooves that run vertically along the belt length.

The serpentine belt delivers mechanical power to critical engine accessories — namely the alternator, the power steering pump, the air conditioning compressor, and (sometimes) the water pump.

Because of what it powers, it’s sometimes referred to as an:

Accessory drive belt
Accessory belt
Alternator belt
Fan belt

Let’s spiral in a little deeper and see how the serpentine works.

What Does The Serpentine Belt Do?

The serpentine belt transmits rotational energy from the engine’s crankshaft to all the engine accessories. The multi-grooved design of the belt helps to accommodate bidirectional flexing while keeping it strong enough to transfer force to multiple loads.

How does it do so?

Each engine accessory (e.g. the air conditioning, power steering, and so on) has a pulley. The serpentine belt acts as a connection between these pulleys to the rotating engine crankshaft. So, as the crankshaft rotates, those pulleys also rotate, powering the accessory.

Most engines will also have an idler pulley set and a belt tensioner.

The idler pulley presses against the back of the serpentine belt, creating enough wrap angle on the accessory pulleys to prevent belt slippage. This is what forms the serpentine shape of the belt.

The belt tensioner helps maintain the belt tension for the serpentine to work optimally. However, older cars without a tensioner pulley need the tension to be set manually.

Here’s the thing.

Engines didn’t always use a serpentine belt, so what makes the serpentine belt a better fit in most modern engines?

What Are The Benefits Of The Serpentine Belt?

The serpentine belt is an efficient, all-in-one solution to the multiple V-belt system in older vehicles.

Here are a couple of benefits to having it under your hood:

A. Consumes Less Engine Space

Serpentine belts consume less engine space as it’s only a single belt running past and powering all the necessary engine accessories.

B. More Tension Without Stretching

A single, wider belt (as opposed to multiple, thinner V-belts) allows more belt tension without stretching.

High tension reduces belt slippage, increasing belt life and efficiency. Reduced slipping comes with the added benefit of being able to use lower-ratio pulleys, which then reduce engine load — improving fuel economy and power availability.

C. One Belt Tensioner Needed

Only one movable belt tensioner is required to manage the belt tension. This means all accessory components can be mounted to the engine without having to swivel.

D. Eliminates Flipping

Using the serpentine belt eliminates the tendency of thinner V-belts to flip over in pulleys, especially when running at high RPMs or when the belt stretches too much.

E. Easier Maintenance

Serpentine belts are easier to maintain and replace as it’s only a single belt to manage. There’s no need to remove multiple V-belts just to replace a faulty one.

While serpentine belts present several significant advantages for your car, there are certain drawbacks such as these:

Serpentine Belt Drawbacks

Nothing is perfect, so even the ingenious serpentine has drawbacks that you should be aware of:

Loss of critical function: A failing serpentine belt (whether it’s knocked loose or breaks) means all critical vehicle functions are lost. The power steering, air conditioner, alternator, and water pump will stop working.

No redundancy: With older multiple drive belt systems, a car can still run if only the power steering or air conditioning fails. However, a broken serpentine belt will stop all critical vehicle peripherals from running.

A failing peripheral affects others: A single failing accessory (like a power steering pump or air conditioning compressor) can cause the entire accessory drive to fail. You might not be able to get the car up and running without fixing that faulty accessory first.

However, the serpentine belt often gives ample visual warning before it fails altogether.

And it will still work acceptably even if it loses all of its grooves.

Now that we’ve gotten down the basics of serpentine belts, let’s go through some FAQs.

7 Serpentine Belt FAQs

We’ve answered seven serpentine belt questions that you might have in mind:

1. Is The Serpentine The Only Engine Drive Belt?

In most modern vehicles, yes.

You might hear the serpentine belt referred to as an accessory drive belt or fan belt, which refers to the individual belts that older drive systems used.

Older cars used individual drive belts (also called V-belts) that could be replaced separately. The problem with multiple belts is that vehicles experienced compromised performance as the individual belts wore down.

The newer serpentine belt winds through multiple pulleys to power all the accessory systems and is much more reliable and efficient as all engine components function simultaneously. Interestingly enough, some vehicles use two serpentine belts.

2. What Are Other Types Of Engine Belts?

In a car that doesn’t use a serpentine belt as a drive belt, you may find these instead:

Alternator belt: This drives the alternator to charge the car battery
Power steering belt: This drives the power steering pump to make steering easier
Water pump belt: Powers the water pump to maintain engine cooling system
Air conditioning compressor belt: Drives the air conditioning compressor to keep the vehicle cabin cool

What about the timing belt?

Unlike the drive belt series, which is located outside the car engine, the timing belt is inside the engine, keeping the engine’s crankshaft and camshaft in sync. Sometimes the timing belt drives the water pump and oil pump too.

It’s easy to tell it apart from a serpentine belt, as the timing belt has distinct horizontal teeth designed to fit cogwheels.

Here’s something to remember: the timing belt often needs replacing about the same time as the serpentine belt.

3. What’s A Belt Tensioner?

Serpentine belts are like a giant, rapidly-spinning rubber band and must retain a degree of flexibility and tension.

The belt tensioner is a self-tensioning device.

It’s designed to hold a predetermined amount of tension on the serpentine belt, allowing the serpentine to function optimally.

The belt tensioner features an internal pulley and spring that applies the necessary tension on the serpentine belt, keeping it tight and preventing it from slipping, running hot, or squealing.

4. How Often Should I Replace The Serpentine Belt?

Modern serpentine belts are made to last a long time. You can expect 60,000-100,000 miles of service on average. Older neoprene belts typically lasted around 50,000 miles, but the newer EPDM belts can function well up to 100,000 miles.

When should you have it looked over?

It’s a good idea to have the mechanic check your car’s serpentine belt during an annual vehicle inspection or an oil change. Alternatively, you can have it reviewed at roughly 50,000-70,000 miles of usage.

5. Why Should I Replace My Serpentine Belt Ahead?

Driving with a worn belt can damage engine accessories as power distribution won’t be optimal, creating unnecessary strain on mechanical parts.

Even if an old serpentine belt looks good, it has a limited lifespan, so replacing it with a new belt can save you money in the long run. You’ll prevent the risk of breakdown and potential engine damage a worn or broken serpentine belt can incur.

6. What Are The Symptoms Of A Faulty Serpentine Belt?

You’ll know there’s a potentially bad serpentine belt in your engine bay when these symptoms crop up:

A chirping or squealing noise: These sounds from the engine bay may indicate a loose belt that’s slipping or a belt and pulley that aren’t functioning correctly. It might be more noticeable when you’re turning a corner when higher torques are needed.

There’s a noticeable vehicle performance loss: Your steering becomes heavy as the power steering pump fails. There’s also a sudden battery drain as the alternator isn’t charging correctly, or worse, your engine stalls.

Signs of belt wear: An old belt will likely display cracking, glazing, or fraying — which all point to imminent belt failure.

The Check Engine light pops on: this malfunction indicator light will glow whenever any engine issue is detected, from a compromised cooling system to low brake fluid levels.

If any of these serpentine belt issues appear, the wisest thing is to get it checked by a professional mechanic and maybe get a new serpentine belt.

7. How Can I Easily Get A Serpentine Belt Replacement?

A serpentine belt replacement isn’t the most complex repair to do, but it certainly involves a fair amount of vehicle know-how and more than just a wrench to loosen nuts.

As such, you’ll want a reliable mechanic to switch out your failing serpentine belt for you.

Even better, if they’re mobile mechanics, like AutoNation Mobile Service, who can install your replacement serpentine belt right in your driveway!

AutoNation Mobile Service is a convenient auto repair and maintenance solution offering these benefits:

Online booking is convenient and easy
Competitive and upfront pricing
Professional mechanics perform auto servicing and inspections
Only high-quality tools and replacement parts are used for all maintenance and repairs
AutoNation Mobile Service provides a 12-month | 12,000-mile warranty for all repairs

Fill this online form for an accurate cost estimate of your serpentine belt replacement.

Closing Thoughts

The car’s serpentine belt is a component that is often overlooked as a source of mechanical issues in aging vehicles. All parts wear down with time and use, and an old belt displays its wear quite obviously before getting close to terminal failure.

So, if symptoms crop up or you’ve hit that 50,000-mile mark, make sure your serpentine belt gets a checkup. With AutoNation Mobile Service around, that’s easily done too!

Just contact them, and their expert technicians will drop by to help you install a new belt.