As the name implies, your car’s serpentine belt snakes around your engine bay, engaging a wide range of pulleys.
It transfers some of the engine’s motion to power critical components like the alternator, water pump, air conditioning system, and power steering pump.
Bad serpentine belt signs often start out with screeching noises under the hood when you start the car and sometimes when you accelerate. They can quickly worsen into problems with weak charging from the alternator, a struggling power steering system, and more.
To find out if you’re truly experiencing bad serpentine belt signs or if there’s some other fault at play, we will have to take a few twists and turns through some technical details.
What is a Serpentine Belt?
Older vehicles have engines with several V-type belts (more on that later), with each of the belts powering at least one component.
The downside of this system is that there is always a need to maintain and replace several belts. The introduction of the serpentine belt changed that.
The engine component known as the serpentine belt is a long, winding belt (hence the name “serpentine) that connects several accessories to the main drive pulley.
The engine turns this pulley, so when you turn your vehicle’s engine, the crankshaft spins, and this motion turns the pulley.
As the pulley rotates, the serpentine belt moves and powers the vehicle’s accessories connected to it: the power steering pump, the radiator fan, the alternator, and the air conditioning compressor, among others.
The serpentine belt is situated outside the engine block and is relatively easy to identify. It is a black, ribbed, snake-like belt on the outside of the engine block. It coils on other vehicle components and is continuously turning for as long as the engine runs.
It can either be tensioned automatically or manually; however, if you drive a modern vehicle, you are more likely to find an automatically tensioned serpentine belt on your engine.
The automatic tensioner serves to keep the serpentine belt at the right tension as it always applies the right amount of tension to the belt.
Without the right tension, the possibility of the serpentine belt slipping and disengaging from the pulley increases. You don’t want that to happen because the engine will stop running after key components powered by the belt no longer work.
Although the average serpentine belt is built to last, how long your serpentine belt lasts depends on the material it was made from.
There are the Neoprene rubber belts and the Ethylene Propylene Diene Monomer rubber, which are built to last about twice as long as the Neoprene belts. Regardless of the material used, at one point, you will need to replace your serpentine belt.
There are several reasons why you might need to replace your serpentine belt. The belt might not be well-adjusted on its pulley; it might be contaminated by fluid or just worn out from frequent use.
Regardless of the reason, serpentine belts almost always let you know when they are about to fail. Detecting symptoms like bad serpentine belt sound or power steering noise and promptly acting on them will save you a lot of problems with your car.
What Does a Serpentine Belt Do?
A serpentine belt is the primary engine belt used on almost all modern vehicles. Older vehicles may instead feature several V-belts, named for their shape that is designed to fit in a single groove on the pulley.
V-belts typically require manual tensioning of one or more accessories to keep the belt tight, and may only be able to run one accessory drive per belt.
Serpentine belts are often the only belt used to operate the engine accessory drive, but in some cases, a second belt may be used for less critical accessories like the air conditioning compressor.
The serpentine belt on your vehicle is a long, reinforced rubber belt that uses the motion of the crankshaft pulley to power the components of the accessory drive system.
Serpentine belts are normally thin and flat with multiple grooves or “ribs” on the inside of the belt that match the rib pattern of the pulleys on the accessory units. These accessory systems may include:
- The Water Pump: Which ensures that coolant is circulated throughout the engine and cooling system to prevent overheating.
- The A/C Compressor: That pressurizes refrigerant that is cycled through the A/C system to provide cold air to the cabin as needed.
- The Power Steering Pump: Which pressurizes power steering fluid for use by the steering gearbox or rack and pinion unit and makes the steering wheel easier to turn.
- The Alternator: Receives power from the serpentine belt that is used to generate the electricity necessary to recharge your battery and operate the engine and electrical system while the engine is running.
Complete failure of the serpentine belt can prevent these systems from receiving power and lead to a variety of symptoms, but even a belt that is too loose or worn may prevent these systems from working optimally.
If you experience overheating, poor A/C system performance, difficulty turning, a battery that fails to charge and causes hard starting, or a combination of these symptoms, inspecting the serpentine belt is a great place to start your diagnosis.
Why Is the Serpentine Belt Tensioner Important?
Most of the vehicles made today have a self-tensioning device. This device is referred to as the automatic belt tensioner. The amount of tension the belt tensioner holds over the serpentine belt is predetermined.
The serpentine belt must maintain a specific balance of tension and flexibility. The tensioner’s internal spring and pulley apply just the right amount of force against the serpentine belt, so it remains tight.
When the amount of tension is insufficient, the serpentine belt slips, makes noise, or overheats. This lack of tension can put your AC, power steering, and other accessories powered by the engine out of business.
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.
#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.
Causes of Serpentine Belt
A serpentine belt goes bad due to one or more of the below-given causes:
- Normal Wear and Tear
- Excessive Load
- Contaminants
- Misalignment
- Improper Tension
- Damaged Pulleys
- Age of the Serpentine Belt
#1. Normal Wear and Tear.
Your serpentine belt may wear out with time because of regular use and exposure to contaminants, friction, and heat. As we discussed above, it is made of rubber. Therefore, it may deteriorate sooner, leading to glazing, fraying, or cracks.
#2. Excessive Load.
If your serpentine belt is exposed to heavy loads beyond its capacity, such as when using aftermarket accessories or modifications that increase power demands, it can cause the belt to wear out more quickly.
#3. Contaminants.
The contaminants such as the transmission fluid, engine oil, coolant, or dirt on the belt may lead to its early failure. However, a leakage from the engine parts, such as a leaking coolant hose or oil seal, may contaminate the belt and speed up its.
#4. Misalignment.
The pulleys on that your serpentine belt move must be properly aligned. If your pulleys are misaligned or have an extreme play, they may ultimately lead to belt failure.
#5. Improper Tension.
If your serpentine belt is not suitably tensioned, it may cause unnecessary slippage or inadequate hold on the pulleys. Insufficient tension may lead to a worn or loose belt tensioner, incorrect installation, or a misaligned pulley.
#6. Damaged Pulleys.
A damaged or worn pulley may lead to uneven wear and excessive friction on the belt, which may lead to premature failure. However, your pulleys may damage due to insufficient maintenance, wrong installation, or debris.
#7. Age of the Serpentine Belt.
With the age of your belt, it may become more vulnerable to wear and failure. The service life of a belt depends on different factors, such as the belt quality, vehicle maintenance, and driving conditions.
Serpentine Belt vs. V Belt
Let’s compare both components.
| Serpentine Belt | V-Belt |
| It is bigger than the V belt and is only used in newer vehicles. You will only find one serpentine belt in a car, and several accessories are connected to it for power. | This belt is thinner and smaller than a serpentine belt and can be found in older vehicle engines, where they are dedicated to one accessory at a time. There are often multiple V belts in an engine. |
| The serpentine belt is less complicated and easier to handle, given its multi-rib design that guarantees less slippage. The distance between the accessories is shorter, so the vehicle’s engine compartment is less clumsy as there are fewer components to deal with. Serpentine belts are generally easy to install and maintain. | It is a lot more complicated to manage the V belts, especially with how the accessories and pulleys are located around the engine. It can be challenging to negotiate so many components when a V belt has to be replaced. |
| You will need to change the brackets and pulleys to pull off a serpentine belt conversion. | The V-belt has a deep V, which helps the belt stay longer on the pulley whenever there is a chance of it slipping. It is designed to fit in the grooves on the pulleys. Its small compact size also makes it great for vertical or horizontal orientations. |
| Serpentine belts are great for long distances since they can handle high RPMs. | V-belts are not designed to handle high RPMs, so they are not a good idea for long distances. |
| You don’t have to re-tension the serpentine belt all the time. All you need is an automatic tensioner that maintains the right tension at all times. | V-belts need to be re-tensioned regularly. |
Serpentine Belt vs. Timing Belt
| Serpentine Belt | Timing Belt |
| The serpentine belt is vital to several engine functions since it powers a lot of engine components. It is designed to connect accessories like the AC compressor, the water pump, the power steering pump, and the alternator. This way, several engine components work in unison while the engine is running. | The timing belt attaches the crankshaft in your vehicle’s engine to the camshaft. The timing belt is responsible for the timing in the operations of the pistons and the valves and cylinders. So any issue with the timing belt will prevent both components from working in tandem and ultimately hamper the vehicle’s engine’s proper functioning. This is one of the loose timing belt symptoms. |
| The serpentine belt is obvious as it is looped around several engine components on the engine’s exterior. It is structured like a snake that twists and turns around different engine parts. | On the other hand, the timing belt is located inside your engine, where it hooks into the gears. |
| As a result of its design and location, it is relatively cheap to replace your serpentine belt. Depending on your vehicle’s brand, model, and year and how you choose to replace your serpentine belt, the cost should be anything between $50 to $200. | Timing belt replacement cost can be high because the timing belt is located within the engine, making it more difficult to access. Depending on the type of vehicle involved, the availability of the kind of belt, and the mechanics you hire, replacement costs for a timing belt can be anywhere around $300 to $500. |
| Serpentine belts have a snake-like form with ribs that allow them to attach to different accessories on both sides. | Timing belts have little teeth that are designed to grip the engines’ crankshaft. You are likely to hear a timing belt noise when this does not happen. You can learn also the Timing belt vs Timing Chain. |
When to Replace Your Serpentine Belt
Mileage Recommendations
Most vehicle manufacturers recommend replacing the serpentine belt between 50,000 to 100,000 miles as part of regular preventative maintenance. Inspections typically begin around the 60,000-mile mark, when early signs of wear might start appearing.
Even if your belt appears to be in good condition, experts suggest replacement at approximately 90,000 miles to prevent unexpected failures.
Immediate Replacement
Replace your serpentine belt immediately if you notice any of these warning signs: squealing or chirping noises from under the hood, visible cracks or fraying on the belt surface, illuminated dashboard warning lights, power steering difficulties.
Or air conditioning failures. Addressing these symptoms promptly prevents further damage to your vehicle’s essential systems and helps you avoid more costly repairs later.
Regular Maintenance
Regular visual inspections serve as the best defense against serpentine belt failures. Checking your belt during routine maintenance appointments allows you to identify potential issues before they escalate into major problems.
These proactive inspections help detect signs of wear including cracks, glazing, or missing chunks of material that indicate the belt is deteriorating.
Catching these problems early not only ensures your vehicle’s reliability but also prevents the safety risks and additional repair expenses associated with a complete belt failure.
How to Fix a Bad or Loose Serpentine Belt?
Fixing a bad serpentine belt typically involves replacing the worn or damaged belt with a new one. Here are the steps to follow:
Tools and Materials Needed
- New serpentine belt (make sure it matches your vehicle’s specifications)
- Socket set with a wrench
- Belt routing diagram (usually found under the hood or in your vehicle’s manual)
- Belt tensioner tool (optional, but helpful)
Step-by-Step Instructions
- Safety Precautions: Ensure that your vehicle is parked on a level surface, the engine is turned off, and the key is removed from the ignition. For added safety, disconnect the negative battery cable to prevent any accidental engine starts.
- Locate the Belt Routing Diagram: Before removing the old serpentine belt, locate the belt routing diagram under the hood or in your vehicle’s manual. This diagram illustrates the path the belt takes around the various pulleys.
- Release Belt Tension: Locate the belt tensioner pulley, which is usually a spring-loaded pulley that applies tension to the serpentine belt. Use a socket and wrench or a belt tensioner tool to rotate the tensioner in the direction specified in your diagram. This action will relieve tension on the belt, making it easier to remove.
- Remove the Old Belt: Carefully slide the old serpentine belt off the pulleys while keeping track of its path according to the routing diagram. Take note of how it wraps around each pulley.
- Install the New Belt: Compare the new serpentine belt with the old one to ensure it has the correct length and rib count, matching your vehicle’s specifications. Begin threading the new belt around the pulleys, following the routing diagram you located earlier. Start with the crankshaft pulley and work your way around, making sure it’s properly seated on each pulley.
- Apply Tension: Once the new belt is in place, use the tensioner tool or a wrench to rotate the tensioner again, allowing it to apply tension to the belt. Ensure that the belt is correctly seated on all pulleys and that it’s aligned properly in the grooves.
- Inspect for Proper Alignment: Double-check that the new serpentine belt is properly aligned and seated on all pulleys. Make sure it follows the exact path shown in the routing diagram.
- Reconnect the Battery: If you disconnected the negative battery cable earlier, reattach it.
- Start the Engine: Start your vehicle and let it run for a few minutes. Listen for any unusual noises or vibrations that could indicate a problem with the belt installation.
- Check Belt Tension: Turn off the engine and recheck the belt tension. The belt should have a slight amount of deflection when pressed with your finger. If it’s too loose or too tight, adjust the tension accordingly.
- Final Inspection: Give the serpentine belt one last visual inspection to ensure it’s properly seated and aligned on all pulleys.
Fixing a bad serpentine belt is a relatively straightforward process, but if you’re unsure about any step or lack the necessary tools and experience, it’s advisable to seek professional assistance from a mechanic or automotive technician.
A properly installed and tensioned serpentine belt is essential for the reliable operation of your vehicle’s engine and its various accessories.
How Do You Test a Serpentine Belt?
If you’ve noticed bad serpentine belt signs, you can perform a layman’s test by pressing your finger down on the belt in the middle of its longest span between pulleys. A serpentine belt in good condition shouldn’t have more than half an inch of movement.
Testing a Bad Serpentine Belt with a Wear Gauge
Newer serpentine belts from EPDM (Ethylene Propylene Diene Monomer) don’t easily show signs of wear and tear like serpentine belts from reinforced rubber.
Rather than looking for fraying and cracks, the best way to test or confirm if an EPDM serpentine belt is bad is to use a wear gauge and the following steps.
- Step One: Turn the engine off and let it cool completely.
- Step Two: Set the belt wear gauge on the serpentine belt so that the ribs on the underside of the belt fit perfectly with the corresponding contours of the belt gauge.
- Step Three: Make sure the belt gauge is thoroughly seated, then apply a light amount of pressure and try to rock the gauge back and forth.
- Step Four: Observe the gauge for 10 to 15 seconds.
If it stays properly seated with little to no movement, your car’s EPDM serpentine belt itself is likely good. Though it probably means that the bad serpentine belt signs you’ve noticed are likely related to some other issue.
This is most likely a failing tensioner pulley or a belt-driven engine component with a misaligned pulley affecting the serpentine belt’s performance.
If the belt gauge rocks back and forth excessively, slides laterally, or lays completely flush against your EPDM serpentine belt, it likely means the belt’s material has degraded to the point that it needs to be replaced.
Though if the belt has less than 50,000 miles on you, you should strongly suspect that one or more pulleys in the engine components or the tensioner arm are the true underlying cause of the bad serpentine belt signs.
What is the lifespan of a serpentine belt?
The average lifespan of a serpentine belt can range from 50,000 to 100,000 miles. Though 65,000 to 75,000 is more realistic in the real world.
Remember that alignment issues with one or more belt-driven components, like the alternator or the power steering pump, can wear out a belt prematurely. An issue with the primary tensioner pulley can also lead to premature serpentine belt wear.
Serpentine Belt Replacement Cost
So how much does it cost to replace a pulley and serpentine belt? The cost of replacing a serpentine belt depends on the make, model, and year of your vehicle on the one hand.
Where you choose to get it done also matters; there will be a difference between serpentine belt replacement cost of firestone and the serpentine belt replacement cost of Valvoline.
Similarly, replacing the serpentine belt in your garage is cheaper than having a professional do it for you.
A significant part of the costs of replacing serpentine belts goes to labor costs. The typical serpentine belt costs around $25 to $75.If you opt to do it yourself, you don’t pay any labor costs.
Having an auto mechanic change the belt can cost you between $100 to $200.It is easy to find out all you need to know about serpentine belt replacement costs. Simply carry out an internet search with the entry “serpentine belt replacement near me.”
FAQs.
Q: What Does A Bad Serpentine Belt Sound Like?
Depending on the vehicle, a bad serpentine sound is similar to a screech, a whine, or a squeal.
Whatever name you give the sound, it is loud and highly unpleasant and is one of the more obvious signs of a bad serpentine belt. Sometimes, this sound gets worse when you drive uphill or try to turn the steering wheel.
Q: Can A Bad Serpentine Belt Cause Acceleration Problems?
Yes, it could. Bad serpentine belts cause loss of power, especially in situations where slippage occurs and the alternator supplies power to the ECM.
In such conditions, the alternator cannot provide the required electrical charge, and as a result, there is a drop in the voltage.
Q: How Do I Know If My Drive Belt Needs To Be Replaced?
Another name for the serpentine belt is the drive belt. There are a lot of signs that indicate that the drive belt in your car is bad. The first step is to know these signs for what they are.
The second step is to carry out regular vehicle inspections by yourself or with a mechanic’s help. Regular checks ensure that you can identify a bad drive belt as early as possible.
Some of the signs you might notice are squealing, whining sounds, a damaged belt, and an overheating engine, among others.
When you are quick to note these signs’ presence, especially bad serpentine belt tensioner symptoms, it becomes easier for you to detect when your drive belt needs to be changed.
Q: What Happens If Serpentine Belt Breaks While Driving?
The vehicle shuts down after a while because the engine can’t operate with a broken serpentine belt. This is because the belt is responsible for a range of functions like steering wheel control.
So when the serpentine belt breaks while driving, a range of things occur. For one, it becomes difficult to control the steering. The battery will die after a while since the alternator can no longer charge it.
The water pump stops working too, so the engine starts to overheat after some time. At a point, the engine will pack up and will require being towed. So yes, a bad serpentine belt cause loss of power.
Q: How Many Years Does A Serpentine Belt Last?
That depends on the material used in making the serpentine belt, how old your vehicle is, the way you drive, and the vehicle’s mileage. The brand of the vehicle also matters because the inspection intervals for different vehicles differ from vehicle to vehicle.
By and large, the type of material used in making the serpentine belt matters a lot. The older serpentine belts that are made from Neoprene rubber do not last as long as the newer, improved belts made from Ethylene Propylene Diene Monomer.
All things being equal, the average serpentine belt can serve you for between 50,000-100,000 miles. With a well-maintained serpentine belt, you don’t have to worry about what causes a serpentine belt to break.
Final Words
The serpentine belt of your vehicle is a thick strip of grooved rubber and metal that winds around several engine accessories that are powered by it. This explains why it is responsible for many engine and vehicle functions.
That said, a bad serpentine belt in your vehicle is something that you do not want to have. Simply put, a broken serpentine belt can be dangerous for you and the health of your engine and vehicle.
Thankfully several symptoms are associated with a bad serpentine belt. So once you can identify bad serpentine belt symptoms, you can manage the situation before it deteriorates.
Your best bet is to have a seasoned automotive mechanic inspect your serpentine belt, belt tensioner, and engine components regularly.