5 Reasons An Alternator Belt May Squeal After Replacement – [Solutions]

You’ve gone through the process of changing the alternator belt, but the belt is squealing after you’ve replaced it. This is a common problem that troubles a lot of drivers and there are a number of reasons why it happens. In this article, we’ll discuss the 5 most common reasons for a noisy alternator belt, and how to fix them. 

The reasons why the alternator belt may squeal are a bad belt tensioner, inadequate belt replacement, a problem with one of the idler or drive pulleys, belt or pulley misalignment, and a bad belt. 

What Is The Alternator Belt?

The alternator belt takes the power from the engine to drive the alternator which in turn supplies the system and the battery with electricity. Older vehicles had fewer auxiliary systems and more space in the engine bay. Because of that, manufacturers could afford to place independent belts for power steering, water pump, and alternator. 

The modern engine layout has systems spread around in a tight space, so instead of using separate belts, a single belt is used to drive everything – the serpentine belt, otherwise known as a drive or fan belt. 

The serpentine belt connects the crankshaft to the A/C, power steering, alternator, and water pump. It also has one automatic belt tensioner and a number of idler pulleys that direct the belt in a certain way. This makes the system much more complex, but despite that, the belt is very durable and reliable.

Reasons Why An Alternator Belt May Squeal

1. Belt Tensioner

The alternator or serpentine belts will stretch over time and parts will wear out slightly to the point where the belt becomes loose. On older vehicles, tension had to be adjusted more often and by hand, but serpentine belts have a spring belt tensioner that does the job for you.  

If you’ve changed the belt without changing the tensioner, the added load will likely cause it to break, as it was already worn down. Whether you’re manually tightening the belt or replacing the tensioner, the process is relatively simple.

Tools You’ll Need: 

	Title	Price	Buy
Top	ACDelco Professional 38278 Drive Belt Tensioner Assembly with Pulley
Top	Powerbuilt Alltrade 648629 Kit 52 Serpentine Belt Tool Set
Top	Stalwart 75-HT3009 Combo SAE & Metric Wrench Set with Carry Case, 22 Piece

Prices pulled from the Amazon Product Advertising API on:

Steps To Replace The Belt Tensioner:

1. Find the belt diagram for your vehicle. Use it to locate the belt tensioner.
2. With the toolkit to detach the old tensioner.
3. Place the new tensioner in place and hold it down while tightening the bolt.

Steps To Tighten The Alternator Belt:

1. Loosen the bolt that holds the alternator in place.
2. Use a large-frame wrench to leverage the alternator and tighten the belt.
3. While maintaining tension with one hand, tighten the alternator bolt with another. 
4. Check the tension. It should not be too tight, otherwise, it might break the alternator or crankshaft pulley.

2. Idler Pulleys

Idler pulleys do not draw power from the crankshaft and are instead used to angle the serpentine belt so it approaches a drive pulley at the right angle. Even though they’re spinning freely, the rotation will inevitably wear out their bearings, which can loosen the belt and cause a squeal. 

Tools You’ll Need: 

	Title	Price	Buy
Top	GEARWRENCH 15 Piece Ratcheting Serpentine Belt Tool Set - 3680D
Top	ACDelco Professional 38001 Idler Pulley , Black

Prices pulled from the Amazon Product Advertising API on:

Steps To Tighten The Idler Pulley:

1. Find the belt diagram for your vehicle. Use it to locate the belt tensioner.
2. Loosen the belt tensioner.
3. Now that the belt is loose, you can now unscrew the idler pulley. 
4. Install the new pulley and position the serpentine belt the right way. 
5. Screw the tensioner in place to finish the job.

3. Belt Misalignment

The serpentine belt has a lot of stops on its way around the system, and each pulley has to be aligned perfectly, otherwise, the belt will warp which will put added stress on it and cause it to squeal. 

Fixing the misalignment requires a laser measuring tool that will show you which of the pulleys is out of alignment. The tool is not that cheap nor is it easy to use, so unless you can rent one from a local store, you’ll have to take your vehicle to a mechanic.

4. Replacement Belt

The problem with replacement serpentine belts is that often they’re not built to the same standard as the original belt. The problem even goes as far as to affect OE replacements, so you have to be really careful when buying a replacement. 

When you’re picking a replacement belt, go with trusted brands. Do some online research and find the best replacement belt for the engine inside your vehicle. Generally, ACDelco, Conti, Dayco, and Gates have high-quality belt replacements. 

	Title	Price	Buy
Top Top	Gates 90K-39185 Complete Serpentine Belt Drive Component Kit
Top	Dayco 5060945 Serpentine Belt
Top	ACDelco GM Original Equipment 12626222 V-Ribbed Serpentine Belt

Prices pulled from the Amazon Product Advertising API on:

Steps To Replace The Serpentine Belt

1. Take a picture of the serpentine belt then release the belt tensioner.
2. Remove the old belt and idler pulleys.
3. Install the new idler pulleys and check the belt mounting diagram for your vehicle.
4. Mount the new belt on, and reinstall the belt tensioner.

5. Drive Pulleys 

Worn drive pulleys are the last possibility, and depending on the system, the most difficult one to fix. It requires special tools and some experience with engine repairs. We’ve already covered how to replace the power steering pump pulley, so in this article, we’ll focus on the alternator.

Tools You’ll Need:

	Title	Price	Buy
Top	13 Pcs Alternator Pulley Tool Kit, Alternator Pulley Removal Tool
Top	Dorman 300-850 Alternator Decoupler Pulley

Prices pulled from the Amazon Product Advertising API on:

Steps To Replace The Alternator Pulley

1. Release the belt tensioner and slide the belt off the alternator.
2. Use the pulley removal tool to detach the old pulley. You can work with the alternator still on the vehicle, or remove it first for better access.
3. The tool can also be used to mount the new pulley. Read the instruction to figure out how to use it properly.
4. Place the belt back on facing the correct way.
5. Screw the belt tensioner back in place.

FAQs

Can a bad alternator cause the belt to squeak? 

A bad alternator can cause belt squeak, or rather, a bad alternator pulley. The serpentine or alternator belt makes contact with the alternator pulley and provides power, but when it wears out and fails, it causes a loss of tension and belt squeak.

How do I make my belt stop squeaking?

Fixing serpentine belt squeak involves either changing the belt or one of the problematic pulleys. In some cases, the misalignment of newly installed pulleys will cause the belt to squeal under tension. I would not recommend using WD40 on the pulleys as that would temporarily solve the problem, but actually, cause damage to the pulleys. 

Is it normal for a new serpentine belt to squeal?

The quality of the serpentine belt isn’t up to the manufacturer’s standard, the new belt may be put under too much tension and squeal because of it. Another reason would be leaving the old belt tensioner that became too worn to maintain the right tension.

Why does my belt squeak until it warms up?

Cold causes shrinkage and condensation on the belt and pulleys. This will cause it to be too tight until it warms up, causing a squeaking noise. It is not necessarily a bad thing, but the squeaking noise could also indicate that the belt has become worn and brittle, and cannot handle the temperature differences as well as it used to. 

Summary

Swapping the alternator belt only to hear it squeaking can be annoying, but by following the steps provided in this guide and eliminating causes, you’ll figure out what’s wrong and restore the functionalities of your engine. VehicleFreak is a website devoted to providing its readers with reliable auto-tips and guides, so whenever you need to find useful information on how to solve a problem, check out our website!

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