Blog Car Care Advice Identifying Serpentine Belt Noise (+8 Reasons for the Squeak)
Car Care Advice

Identifying Serpentine Belt Noise (+8 Reasons for the Squeak)

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Is your car making a strange noise?
The serpentine belt could be the culprit! 

But how can you tell for sure?

To answer this, let’s learn how to identify serpentine belt noise, what causes it, and what to do about it.

This Article Contains: 

Let’s start.

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 noise, keep an eye out for these signs:

Note: A bad serpentine 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 belt, check it immediately, as the serpentine belt directly influences vital engine components like your alternator and power steering. 

So, what could have caused the serpentine belt to go vocal? 

Serpentine Belt Noise: 8 Common Causes

If the high-pitched squealing continues while the engine is running, the causes could include:

1. Cold Weather

What if you only have a squealing serpentine belt when 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, creating a belt squeal. 

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 to confirm the cause for the squeaky belt and find out if you’ll need a serp belt replacement to eliminate that annoying squeal.

2. Worn Belt or Dry Serpentine Belt

Belt wear occurs over time, but cars often have more durable belts today (engine belt, alternator belt, timing belt, etc.)

However, you should have your old belt replaced with a new belt after around 75,000 miles

Serpentine belt noise can also come from a fan belt that has started to dry out due to heat, age, or environmental factors. Constant friction 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 serp 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 (alternator belt) that causes the squeal?

The whole pulley system comprises the crankshaft pulley, alternator pulley, and power steering pulley, with tensioner pulleys maintaining belt friction. The crankshaft pulley (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 more of a chirp. If you hear a whining or rumbling noise, it’s likely the harmonic balancer. 

Belt wear is unavoidable and eventually leads to cracks, reducing the belt tension and creating 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

Engine coolant helps regulate your engine through extreme temperatures. However, coolant can damage a serpentine belt or drive belt. 

Once it sinks into the belt, it damages it 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 Due to Improper Installation

The noisy serpentine belt could result from improper installation. The drive belt needs high tension to function correctly. If the replacement belt isn’t installed properly, even an OEM belt isn’t immune to the squealing noise.

Fortunately, it’s easy to detect. 
If you’ve had a new serpentine belt installed and you hear a squealing noise, it may be due to improper installation. 

Let your mechanic check the rubber belt and determine if there’s a misaligned pulley or belt tensioner. 

6. Bad Idler Pulley

If your belt looks fine, it 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 accessories, including the alternator, power steering pump, and AC compressor.

The idler pulley holds the serpentine belt in place with the proper tension. If it doesn’t, the belt may slip, and the annoying squeal will start.

Call a mechanic to check the tension on the idler pulley. It’s also a great opportunity to identify a bad bearing inside the idler pulley that may add 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 the belt 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. Belt Slippage

Slippage can be due to belt tension loss, a weak automatic tensioner, or wrong pulley alignment.

When the belt slips, the friction between the belt and accessory drive pulleys causes the drive belt to overheat, producing a high-pitched squealing noise. Ignoring the belt 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. 

Final Thoughts

A squeaking noise could come from the car’s serpentine belt. However, it could also come from the crank pulley, power steering pulley, alternator pulley, or timing belt. 

If it’s an old 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 belt replacement 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.