That squealing under the hood when you start your car in the morning is no harmless noise. It’s an audible clue that your serpentine belt needs attention. This vital belt powers vital accessories like the alternator, AC compressor, and power steering pump by linking them to the crankshaft’s rotation.
When this drive belt starts glazing, cracking, or slipping, the result can be a variety of issues. Heeding the signs of a bad serpentine belt right away can help you avoid being stranded with a disabled vehicle and an expensive repair bill down the road.
What is a Serpentine Belt?
A serpentine belt, also called a drive belt, fan belt, or accessory belt, is the main engine belt that you see when you open up the hood of your car. These belts are easily identifiable by their distinct ridges that run the length of the belt on one side. The ridges help maintain grip when turning the accessory pulleys.
Serpentine belts are different than timing belts, which are usually not visible just by popping the hood. You usually have to tear down part of the engine to reach the timing belt.
Engine accessories need to get their power from somewhere, and it may surprise you to learn that that place is not the battery. As your engine runs, the spinning motion of the crankshaft is transferred to each of the accessory pulleys via the serpentine belt.
If your vehicle is supercharged, the serpentine belt also powers the supercharger.
Serpentine Belt vs V-Belt
Older engines have v-belts instead of serpentine belts. These are thinner and smaller than serpentine belts and usually connect one accessory to the crankshaft. You’ll often see multiple v-belts in an engine, but only one serpentine belt. Both types of belts serve a similar purpose.
Common Bad Serpentine Belt Symptoms
A bad serpentine belt is not the type of maintenance you want to defer. A snapped serpentine belt could leave you stranded. If the alternator pulley stops spinning, there’s no way to charge the battery.
Several signs will present themselves when a serpentine belt is starting to wear out. Below are some of the most common symptoms of a worn serpentine belt.
1) No Air Conditioning
A malfunctioning air conditioner can be attributed to a lot of things. Since the serpentine belt keeps the air conditioner functional, a bad serpentine belt will take that function away from it.
If you turn on your air conditioner and see that it does not blow out cool air from the air vents, this could possibly be due to a bad serpentine belt.
2) Squealing Sounds
If the front area of your vehicle makes squealing sounds, then your serpentine belt might be misaligned or slipping. Sometimes it might just take a realignment or proper tensioning of your serpentine belt to fix this problem.
In other cases, the belt is probably damaged and will need to be replaced.
See Also: Common Causes of Serpentine Belt Noise
3) No Power Steering
The serpentine belt allows the power steering system to function properly. Power steering is what gives drivers the ability to smoothly steer their vehicle without needing to apply too much arm strength.
If you have a bad serpentine belt, then it will be harder to move the steering wheel to steer your vehicle.
This issue could also be caused by low power steering fluid. While you’re under the hood, check to make sure the power steering reservoir has the recommended level of fluid.
4) Flapping or Scraping Sound
If your serpentine belt is loose or frayed, you may hear a rhythmic flapping or scraping sound in the engine bay. This sound is often correlated to each revolution of the engine. As you give the car gas to raise the engine speed, this rhythmic sound should speed up. Sometimes it gets louder, too.
Sometimes a loose serpentine belt can be fixed by adjusting or replacing the serpentine belt tensioner. In some cases, you will need a new serpentine belt.
5) Visible Cracks on Belt
The serpentine belt is easy to access in most cars. If you want to know if your belt is bad, simply open the hood and look at the belt for yourself. If you notice visible cracks or damage to anywhere on the belt, this means the belt is bad and needs to be replaced right away.
6) Dead Battery
If you’re driving along one day and suddenly lose power, check under the hood to see if your serpentine belt is still attached. Even if you’re able to get the car started, a snapped serpentine belt will not allow the alternator to charge the battery.
Without the alternator’s charge, your car will eventually die from the electricity used by the spark plugs, the radio, and the headlights. A vehicle can often run without a working alternator for a bit of time, but not for long.
If the belt is too loose to maintain grip on the alternator pulley, you may experience a similar symptom as a snapped belt.
7) Pulley Whine
If you start to notice a whine from the engine that changes with engine speed, you may want to have the tension of the serpentine belt double checked. A belt that is too tight puts too much load on the bearings in each of the accessory pulleys and can often cause premature failure of those components.
One of the most common failure modes for engine accessories is actually bearing failure, caused by a serpentine belt that was too tight. If you think your belt may be too tight, it’s best to address this issue as soon as possible to prevent expensive engine damage to peripheral components.
8) Engine Overheating
For engines where the serpentine belt is driving the water pump, this is going to be the most important symptom. If the serpentine belt becomes damaged or worn out, it can slip or break, which can cause the water pump to stop functioning properly.
When the water pump isn’t working, coolant is not circulated through the engine, and the engine can quickly overheat. Overheating can cause damage to engine components, such as the cylinder head, head gasket, and engine block, which can be expensive to repair or replace.
Serpentine Belt Replacement Cost
It is very inexpensive to replace a serpentine belt, fan belt, AC belt, or power steering belt whether it’s broken or loose. The replacement cost of a drive belt is only going to be between $100 and $200 in most cases. The belt itself will cost between $30 and $90 while the labor costs will probably be between $150 and $200.
The ease of accessing the serpentine belt will determine how much the labor costs are. Some model vehicles have the serpentine belt easily accessible, which means the labor should take under one hour. But if the belt is in a more complicated area, it could take about 2 hours.
Easy to reach belts can actually be changed at home with minimal tools. Some belts can be removed by loosening one bolt, while others have a belt tensioner you have to pull on with a wrench to give the belt some slack. You might consult a repair manual for your specific vehicle to see if you can do this yourself.
Either way, this is certainly one of the cheaper components of an engine that you will ever have to replace. It is better you replace this immediately than risk more expensive components getting damaged.
Regularly inspect your serpentine belt for any signs of wear or damage, such as cracks, abrasions, or separation. This will help you identify issues early and avoid any unexpected breakdowns or costly repairs.
To keep your serpentine belt in good shape, you’ll also want to regularly check its tension. A loose or improperly adjusted belt can lead to slippage and premature wear, while a belt that’s too tight can cause strain on the engine’s components.
It’s also a good idea to periodically clean your serpentine belt, as grime and oil can contribute to wear and tear over time and cause noise. To clean your serpentine belt:
- With the engine off, spray some engine degreaser on the belt and the pulleys driving it.
- Allow the degreaser to sit on the belt for a couple minutes.
- Completely rinse off the degreaser using a garden hose being careful not to spray water on sensitive parts of the engine. You may even rinse the belt off with the engine running and then allow it to run until fully dry.
Frequently Asked Questions
What Happens When a Serpentine Belt Breaks While Driving?
If your serpentine belt breaks while driving, the first thing you’ll notice is a sudden loss of power steering, making it harder to turn the wheel. Your air conditioning may stop working, and the engine might start to overheat because the water pump is no longer circulating coolant.
The alternator could also stop charging the battery, potentially causing warning lights to appear on your dashboard. It’s important to pull over and shut off your engine immediately if you suspect a broken serpentine belt, to prevent further damage.
Can Serpentine Belt Issues Affect Acceleration?
Yes, serpentine belt issues can affect acceleration. A worn or damaged belt may slip along the pulley system due to inadequate tension, creating a screeching sound when starting the engine or accelerating hard.
This slipping can cause a decrease in power provided to various systems in your vehicle, such as the power steering, alternator, and air conditioning. This loss of power can result in reduced performance and hinder your car’s acceleration ability.
How Long Do Serpentine Belts Last?
The typical lifespan of a serpentine belt varies depending on the make and model of your vehicle, as well as the type of belt used. On average, you can expect a standard serpentine belt to last about 60,000 to 100,000 miles.
It’s a good idea to consult your vehicle’s owner’s manual for the manufacturer’s recommended service intervals when it comes to drive belts.
How Much is a Serpentine Belt?
A serpentine belt will cost somewhere in the range of $30 to $90 in most cases. If you’re changing it out yourself, this is all it will cost but if you’re paying for someone else to replace it, expect another $150-$200 in labor costs.
How Does a Bad Belt Tensioner Impact the Serpentine Belt?
A bad belt tensioner can have a major impact on the serpentine belt since its job is to maintain proper tension on the belt. If the tensioner is damaged or worn, it may not be able to keep the proper tension, potentially causing the belt to slip, wear out prematurely, or even break.