Is your car making a strange noise?
The serpentine belt could be the culprit!
So how can you stop that unpleasant noise once and for all?
We’ll explore the underlying causes of serpentine belt noise and how to address them effectively. We’ll also share some easy serpentine belt maintenance tips that might save you a trip to the repair shop.
This Article Contains:
- How to Identify Serpentine Belt Noise
- Serpentine Belt Noise: 10 Common Causes
- How to Fix Serpentine Belt Noise
- How to Keep Your Serpentine Belt in Top Shape
How to Identify Serpentine Belt Noise
There can be several reasons why you hear a squealing noise when you drive.
To identify a serpentine belt (aka alternator belt) noise, watch out for these signs:
- Check if the squeaking noise persists and where it’s coming from. If it’s in front of your vehicle (from the engine bay), the squeal is likely from the serpentine belt.
- The squeaky belt can get louder when accelerating or making sharp turns. Rain or humidity can also make it worse.
- You’ll see other systems struggling, like the alternator, water pump, power steering pump, etc. For instance, if your engine often overheats and makes a rattling or squeaking noise, the water pump is failing.
- If a lack of power steering accompanies the squealing noise, the strange noise is likely coming from a bad serpentine belt.
- The air conditioning (AC) may not operate if there’s a serpentine belt issue. A drive belt issue can reduce the power sent to the AC compressor.
NOTE: A bad or noisy belt alone won’t set off any dashboard lights, so it’s important to be alert for any failings in your car’s system.
If you detect a squealing serpentine belt, get it checked immediately. The belt directly influences vital engine components like the alternator and power steering.
So, what could have caused the serpentine belt to go vocal?
Serpentine Belt Noise: 10 Common Causes
If the high-pitched squealing noise continues while the engine is running, it could be due to:
1. Cold Weather
What if your serpentine belt only squeals when it’s cold?
The weather can determine how your car’s serpentine belt performs, especially on a cold morning. Cold temperatures can make the rubber belt brittle, producing that squealing noise.
You probably don’t have a bad belt if the squeak is louder on a cold morning but dissipates as the engine warms up.
However, get it checked by a mechanic and find out if you’ll need a serpentine belt replacement to eliminate that annoying belt squeal.
2. Worn or Dry Serpentine Belt
Even though cars have more durable belts today (engine belt, alternator belt, timing belt, etc.), belt wear can occur over time. That’s why it’s best to replace your old belt with a new one after around 60,000 to 100,000 miles.
The noise can also come from a fan belt that has started to dry out due to heat, age, or environmental factors.
Constant friction amongst car parts eventually causes belt wear, creating that strange noise. This can weaken the serpentine belt to the point where it can’t properly maintain the required tension to grip each tensioner pulley.
Additionally, if a pulley slips, it can cause the serpentine belt to slip, which produces that annoying squealing sound.
It helps to pop the hood and look for a potential belt issue. If you see any cracks, you likely have a dried belt. Replacing it is the only way to stop the serpentine belt noise.
3. Worn Out Pulley or Wrong Pulley Alignment
Did you know it’s not just the serpentine belt that causes the squeal?
The pulley system comprises the crankshaft pulley (or crank pulley), alternator pulley, and power steering pulley, with tensioner pulleys maintaining belt friction. The crank pulley is the main driving pulley, while the harmonic balancer dissipates vibrations created by the crankshaft.
If any tensioner pulley begins to wear out, it’ll create a chirping noise. And if you hear a whining or rumbling noise, it’s likely a worn-out harmonic balancer.
Belt wear eventually leads to cracks, reducing the belt tension and resulting in a noisy serpentine belt. However, belt spray or belt dressing can improve the lifespan of the pulleys.
Fortunately, qualified mechanics can fix this belt issue quickly.
4. Exposure to Coolant
Coolant helps regulate the engine temperatures. However, coolant leaks can damage an EPDM belt (a serpentine belt made from ethylene propylene diene monomer rubber).
Once the coolant sinks into the EPDM belt, it damages the belt immediately, and you can’t wash it off. Even though belt dressing can help reduce the squealing or squeaking noise, if coolant is the culprit, you’ll likely need a replacement belt.
5. Misaligned Belt from Improper Installation
A noisy serpentine belt could be the result of improper installation. Since the drive belt requires high tension to function correctly, even an OEM belt can produce a squealing noise if installed incorrectly.
Fortunately, it’s easy to detect.
If you’ve recently installed a new serpentine belt and hear a squealing noise, let your mechanic check the rubber belt. This will help them determine if there’s a misaligned pulley or belt tensioner.
6. Bad Idler Pulley
Sometimes, there could be an issue with the idler pulley.
What’s an idler pulley?
This pulley regulates the belts connected to the crankshaft and helps move numerous engine parts, including the alternator and power steering pump.
The idler pulley holds the serpentine belt in place with the proper tension. If it doesn’t, the belt may slip, producing an annoying squeal.
Call a mechanic to check the tension on the idler pulley. It’s also a good opportunity to spot a worn bearing inside the pulley, which could be contributing to the belt squeal.
7. Bad Tensioner or Tensioner Bearing
The belt tensioner plays a crucial role in maintaining the correct level of belt tension, keeping the serpentine belt operating normally. The tensioner bearing attaches to the belt tensioner, ensuring it can apply pressure as the belt rotates.
Maintaining proper tension is essential. Without it, a serpentine drive belt will start to slip, producing a noise. A worn-out belt tensioner can become too weak to keep the serpentine belt in place, causing the belt to slip off the tensioner.
How can you tell if you have a loose serpentine belt or tensioner?
You’ll hear the belt noise when you turn the wheel sharply or accelerate.
If the hydraulic belt tensioner is broken or damaged, you may spot a tensioner leak or hear a rattling serpentine belt noise.
8. Slipping Belt
Slippage can be due to belt tension loss, a weak automatic belt tensioner, or wrong pulley alignment.
A slipping belt creates friction between the belt and the accessory pulley. This causes the drive belt to overheat, producing a high-pitched squealing noise. Ignoring the noise can cause the belt to slide off the pulleys, affecting key engine components.
Using belt spray can help improve the grip the serpentine belt has on the pulleys.
9. Harmonic Vibrations at a Specific Speed
Sometimes, the serpentine belt may resonate at certain revolutions per minute (RPM), producing a squealing or chirping noise. This happens when engine vibrations align with the belt’s natural frequency, especially if the tensioner is weak or worn.
You may feel these vibrations through the steering wheel or gas pedal. To help isolate the cause, try shifting the vehicle into neutral — if the noise stops, harmonic vibration could be to blame.
10. Issues with a Belt-Driven Component
A failing accessory component, like the AC compressor, power steering pump, or alternator, can stress the serpentine belt and cause squealing. This often happens when a pulley’s bearing becomes rough or worn.
To confirm this, turn off the engine and let it cool, then remove the belt and spin each pulley (including the power steering pulley, alternator pulley, idler pulley, and others) by hand.
If any pulley feels rough, resists movement, or makes noise, the component likely needs to be repaired or replaced.
Whatever the underlying cause may be, a qualified mechanic can help eliminate that annoying noise for good.
Let’s look at some of the fixes they might use.
How to Fix Serpentine Belt Noise
Here’s how your mechanic will tackle each issue causing the belt noise:
- Tension problems: If the belt isn’t maintaining proper tension, they’ll either tighten or replace the belt tensioner. First, the mechanic will check if the pulley spins freely and the tensioner arm moves smoothly through its full range. They’ll replace the tensioner if they feel roughness or notice a weak spring.
- Misalignment issues: Your mechanic will use a straight edge or laser alignment tool to check for any misaligned pulley. They’ll ensure every accessory pulley is securely mounted and not warped or loose. Misalignment from components like the power steering pump or a worn harmonic balancer can also create belt noise.
- Damaged or old belt: If the belt has visible cracks, glazing, fraying, or worn ribs, your mechanic will recommend replacing it immediately. During the replacement, they will also inspect the tensioner, pulleys, and other belts for wear.
- Harmonic vibrations: If resonance at certain speeds causes a chirping noise, your mechanic will first check for vibrations felt through the steering wheel or gas pedal. Next, they’ll inspect for weak belt tension or worn engine mounts and replace them if needed.
- Faulty belt-driven components: If a belt-driven part, such as the alternator, AC compressor, or power steering pump, fails, it can create excess drag or bearing noise. Your mechanic will remove the belt and spin each pulley by hand. They’ll repair or replace any pulley that feels rough, makes noise, or has excessive play.
- Contamination: If the serpentine belt is exposed to fluids like motor oil, power steering fluid, antifreeze, or even belt dressing, it can damage the belt’s surface. Since a contaminated belt can’t be cleaned, they’ll install a new belt.
- Low-quality belt: A poorly manufactured or incompatible belt can cause noise even when all other components are in good condition. That’s why mechanics always recommend a high-quality belt that meets your vehicle’s OEM (original equipment manufacturer) specifications to ensure proper fit and performance.
Next, we’ll go over some basic maintenance checks you can perform to avoid visiting the mechanic.
How to Keep Your Serpentine Belt in Top Shape
For a well-functioning serpentine belt, follow these tips:
- Keep the engine bay clean: Dirt, debris, and fluid leaks can accelerate belt wear, so regularly clean the engine bay.
- Warm up your engine in cold weather: Letting your engine idle for a minute on cold mornings helps reduce sudden stress on the belt.
- Avoid overloading accessories: Don’t switch on accessories, like the AC, defroster, and headlights all at once, as it can stress the belt.
- Listen for early warning sounds: Pay attention to subtle changes in noise, like a faint chirp or fluttering. These can signal early issues before full squeals develop.
- Check belt routing after service: After any engine or repair work, double-check that the belt is routed correctly and hasn’t been twisted.
Say Goodbye to Your Squeaky Belt Today
What starts as a faint chirp or squeal often escalates. The longer you wait, the more likely you’ll end up needing more expensive repairs.
If it’s an old serpentine belt, your best bet is to have a mechanic install a new belt and inspect the pulley system.
Why not let AutoNation Mobile Service handle it?
We’re a mobile auto repair solution, and our mechanics can fit an OEM serpentine belt right from your driveway. We also offer easy online bookings and a 12-month | 12,000-mile warranty on all services.
Contact us for all your car maintenance and repair needs.