What Happens If My Car’s Serpentine Belt Breaks?

The accessory belt (most commonly known in English as the serpentine belt) is a belt that harnesses the rotational motion of the crankshaft to power various vehicle systems, such as the water pump, power steering, or alternator. This component goes by several names, so depending on where you live, you might know it as a ‘serpentine belt’, ‘fan belt’, ‘alternator belt’, or ‘drive belt’.

To function properly, this component requires regular maintenance. Essentially, you need to replace the belt with a new one after a certain number of miles or kilometers. Otherwise, it could snap and trigger numerous engine problems. A broken serpentine belt is not as catastrophic as a broken timing belt, but that doesn’t mean we should take it lightly. If the serpentine belt breaks while the car is in motion, you will almost certainly have to pull over and call a tow truck.

What happens when the serpentine belt breaks?

The serpentine belt is built to last and isn’t prone to sudden failure. However, it wears down over time and with use. Every car has its own replacement intervals, but it is standard practice to replace it at the same time as the timing belt and water pump.

If your serpentine belt breaks while you’re driving, you will probably hear some slapping or thudding noises coming from the engine bay as it comes loose and whips around before falling off. Since this drive belt powers several essential engine systems, here is what will happen if it breaks:

Loss of power steering

If you’re young, you might never have experienced just how absurdly difficult it was to turn a steering wheel a few decades ago. The reason you can steer the wheels of your 2-ton SUV so effortlessly is an engineering marvel called ‘power steering’. If the serpentine belt snaps, the hydraulic system stops working, meaning you’ll have to use a tremendous amount of physical force just to turn the steering wheel.

This issue won’t be as noticeable at high speeds. However, the slower you go, the heavier the steering wheel will feel. In fact, if you have to parallel park the car in this condition, you can skip your afternoon gym session because you’re definitely going to be sore the next day. That being said, it goes without saying that no driver in their right mind wants to lose power steering, especially nowadays when the most popular cars on the road are quite heavy.

Loss of the vehicle’s electrical systems

The serpentine belt drives the alternator. The alternator powers all of the vehicle’s electrical systems and recharges the car battery. If the serpentine belt breaks, the alternator stops generating electricity.

When that happens, your headlights will dim. The radio will cut out, and the battery will drain in record time, as it becomes the vehicle’s sole source of electrical power. The battery warning light on your dashboard will also come on because the battery is no longer charging.

The car’s air conditioning will also stop working if this happens—though thankfully, you’ll still be able to roll down the windows as long as you have some battery power left. Exercise extreme caution if the belt snaps while you’re on the highway on a rainy day. Before you lose your headlights, windshield wipers—and engine power altogether—the smartest move is to pull over, call a tow truck, and not take any chances.

The coolant pump stops working

Without the serpentine belt, the coolant pump (water pump) cannot do its job. As a result, the engine will begin to overheat rapidly.

The temperature gauge will climb into the red zone, and the Check Engine light will illuminate once temperatures exceed safe operating levels.

Some cars are spared this particular issue if their water pump is driven by the timing belt rather than the serpentine belt. Either way, driving with an overheating engine is strongly discouraged, as you’re practically asking for the engine to seize. Fortunately, in modern cars, the engine will shut itself down to prevent catastrophic damage.

Engine enters limp mode

This ties directly into what we just mentioned in the previous paragraph. Your car’s ECU (Engine Control Unit) is quite smart. As soon as it detects faults caused by a broken serpentine belt, it will restrict engine performance to prevent self-damage. To do this, it switches to a much safer operating mode (“limp mode”), limiting power output and illuminating a bright ‘Check Engine’ or engine fault warning light on your instrument cluster.

What should I do if the serpentine belt breaks while I’m driving?

As you may have guessed from what we explained in the previous section, the car isn’t necessarily going to come to a dead stop right away. Even so, you should pull over and park in a safe place as soon as possible. The sudden heavy steering and the risk of engine overheating are more than enough reason to stop immediately rather than push your luck.

Once you have pulled over in a safe spot, call a mechanic or roadside assistance. Additionally, if the broken serpentine belt is dangling inside the engine bay, carefully remove it before moving the vehicle elsewhere to prevent it from tangling and causing further damage.

How long can I drive with a broken serpentine belt?

A couple of factors influence the answer to this question, but on average, your car should be able to run for between 20 and 90 minutes, albeit with severe limitations.

The engine will overheat much faster without a working cooling system on a hot day, giving you a much shorter driving window. If it’s cold outside and your battery is fully charged (and your water pump is timing-belt driven), you might be able to keep the engine running for a little over an hour—just long enough until the battery dies. That’s usually enough time to reach a safe spot or limp the car into a nearby repair shop.

If you find yourself in this predicament, try to turn off all non-essential electronics to minimize battery drain.

Can a car start with a broken serpentine belt?

Yes, a vehicle can start with a broken serpentine belt, assuming the battery still has a sufficient charge. The starter motor and ignition system draw power directly from the battery to crank the engine and initiate the combustion process.

However, you won’t get very far. Your two major limiting factors will be how long the battery charge lasts and how quickly the engine overheats and shuts down.

Symptoms of a damaged or failing alternator belt

The good news is that the serpentine belt shows clear signs of wear long before it actually snaps. Here are a few symptoms to watch out for:

• Squealing or chirping noises coming from the engine bay: This high-pitched sound can be a sign that the serpentine belt is slipping on the pulleys, meaning it either lacks proper tension or is worn out.
• Cracks, fraying, and visible damage on the belt: These are clear visual signs of wear on a serpentine belt. If you spot any of this damage, the belt likely needs to be replaced soon to avoid an imminent breakdown.
• Fluid leaks or leaking hoses: Fluid leaks can point to an issue with the belt tensioner or nearby hoses. If fluid drips onto the belt or tensioner, the tensioner may fail to maintain proper grip and tension, which can lead to premature belt failure.
• Electrical glitches, heavy steering, or engine overheating: While these symptoms are unmistakable once the belt has completely snapped, they can also appear intermittently if the belt is loose or badly worn.

If you notice any of these warning signs, don’t ignore them—call your trusted mechanic right away.

Can I drive with a worn serpentine belt?

Technically you can, but it is strongly discouraged. There is no reason to put your vehicle and your own safety at risk by driving with a deteriorating serpentine belt. Belt failure can happen at any moment, and the consequences on the road can be dangerous.

A serpentine belt typically requires inspection and replacement every 100,000 to 150,000 kilometers (roughly 60,000 to 90,000 miles) of use. Being proactive about having an aging belt inspected and replaced can save you the hassle and potential danger of being stranded with a snapped belt.

Causes that accelerate serpentine belt wear

Serpentine belt issues are typically caused by one or more of the following factors:

• Exposure to heat and friction over time: Because the serpentine belt is in constant motion and exposed to high temperatures inside the engine bay, it is subjected to continuous heat and friction wear. Over time, this ongoing exposure causes the rubber to degrade and eventually snap.
• Faulty belt tensioner: The belt tensioner is essential for keeping the serpentine belt at the proper tension. If this component is faulty, the belt may slip or even come off completely, causing the engine’s belt-driven accessories to stop working.
• Pulley misalignment: Pulleys are designed to guide the serpentine belt smoothly and efficiently. If a pulley becomes misaligned, it can cause uneven belt wear, reduce efficiency, and ultimately lead to belt failure.
• Worn or faulty bearings in the tensioner, idler pulley, or even a belt-driven accessory: Bad bearings create extra friction and misalignment, which can cause the belt to slip, overheat, or snap. Furthermore, faulty bearings inside the engine accessories themselves can cause those systems to malfunction or seize.

What are the ‘idler pulley’ and the belt tensioner?

The idler pulley helps create a sufficient wrap angle around the other pulleys to prevent the belt from slipping. Meanwhile, the belt tensioner (or automatic tensioner) applies the constant tension needed for the serpentine belt to operate smoothly and efficiently.

Just to clear up any confusion, the tensioner we are talking about here is different from the timing belt tensioner. The timing belt and the serpentine (accessory) belt are two separate components: the timing belt synchronizes the crankshaft and camshafts inside the engine, while the serpentine belt drives the external auxiliary systems that work alongside the engine, such as the alternator and the water pump.