How To Replace A Serpentine Belt

The serpentine belt is a deceptively simple component in the overwhelmingly complex series of parts that make up your car's engine. Once upon a time, every component in a car was driven by a separate belt, and some had three or more belts to power everything from the alternator to the air conditioner to power steering. Much later, vehicle engineers determined a way to use a single belt to organize all of these items - a more efficient way to run the engine.  It was the serpentine belt. Let's examine the role the serpentine belt plays in your engine, the signs and symptoms that it may need replacing, and the process of how to replace a serpentine belt when it goes bad.


Tools You Will Need

There are a few specialty tools that are inexpensive and simplify the process of changing your serpentine belt.

  • Serpentine Belt Gauge
  • Serpentine Belt Replacement Tool
  • Serpentine Belt Tool
  • A New Serpentine Belt

While you can replace your belt with regular hand tools, it's not recommended due to how tight the spaces are. Because of this, a serpentine belt tool is essential to loosen the tensioner, and a belt placement tool is needed to help position the belt. Using these tools, you may be able to do the entire job in less than a half-hour from the time you remove the belt to the time you re-engage the tension on the new one.

The serpentine belt tool has an assortment of socket sizes to fit just about any car and has multiple extension bars to allow you to reach your tensioner at the ideal angle while having the best possible leverage to release the pressure. The belt placement tool allows you to easily remove the old belt and replace the new one without needing to reach into the pulleys.


About the Serpentine Belt

Your car's serpentine belt is a single, long belt made of rubber and metal that uses a series of pulleys to drive the car's air conditioning unit, power steering, water pump, crankshaft, fan, and alternator. On some vehicles, even the power brakes can be run by the serpentine belt, and some vehicles may have more than one such belt.

The serpentine belt ensures that all of these components work smoothly and seamlessly together with the correct amount of tension to keep the whole vehicle running at peak performance. The key pulley for the serpentine belt is called the tensioner, and it's a spring-loaded component attached to the engine block whose job, as you may guess, is to keep the belt at the proper level of tension to drive the other pulleys and gears. The car's crankshaft provides the power that turns the belt.


How Long Does the Serpentine Belt Last?

Because the serpentine belt does so much work, it's built to last for many thousands of miles. Still, over time, the belt and the tensioner will inevitably wear out. The tension spring can become worn so it doesn't provide the necessary pressure to tighten the belt. The belt, in turn, can wear out and become misaligned or slip, which can put additional stress on the different parts of the engine, causing premature wear on those components.

Each car has a recommended interval for replacing the serpentine belt, which is often included in your vehicle's maintenance schedule. Still, how often you drive, environmental conditions, and general upkeep can all have an effect on it. That's why it should be inspected regularly for signs of wear and tear, and replaced when needed.


Inspecting Your Serpentine Belt

The first step in inspecting your serpentine belt is to know how it is constructed. It's made of hard rubber with metal fibers molded into it for strength and durability. As the belt ages, the rubber gets brittle and begins to crack. This is the first thing you should look for as you examine the belt.

Next, check the outer edge to see if it looks rough or frayed. Outside wear on the belt is often a sign of misalignment, which can be due to a failing or warped pulley, or a loose accessory which also may need to be addressed. After this, check for splitting or missing ribs. If you see large pieces of rubber missing, the belt is starting to fail and must be replaced.

Finally, check for looseness in the belt. A loose belt with more than a half-inch of movement between pulleys may need to be tightened, or it may be stretched and need to be replaced.

Using a Serpentine Belt Gauge

If you have a newer car, you'll need a different method to inspect it for wear. Many modern serpentine belts won't overtly show signs of wear. This can mean that the belt looks just fine all the way up until it fails. With a tool called a serpentine belt gauge, you can check between the rib grooves to measure their depth. As the belt wears, the grooves will get deeper as the rubber wears. When they are too deep, it's time to replace the belt.


Bad Serpentine Belt Symptoms

When your serpentine belt is damaged, the whole functionality of your car, truck, van, or SUV can be compromised. You'll want to look for any of these symptoms that could indicate your belt is wearing down, damaged, or broken:

  • Squealing sounds - Squealing sounds from the front end of your vehicle could be a sign that your belt is slipping or misaligned. Squealing signs are most often the first warning sign that there's an issue, though it could also indicate that you have misaligned pulleys or a seized tensioner as opposed to a bad belt. In some cases, the belt just needs to be realigned to fix the issue. In others, it could be that the belt is worn or damaged and has to be replaced.
  • Lack of air conditioning - This can be caused by a lot of different factors. One of them, however, is certainly a bad serpentine belt. If you turn on the AC and cold air doesn't blow from the vents, the belt is one thing you'll want to check.
  • Loss of power steering - Again, there are a number of things that could result in loss of power steering, including a fluid leak and bad hoses. One such cause, though, is a bad serpentine belt. Since the belt helps to drive the pressure in the steering pump, a bad belt can make it difficult to turn the wheel.
  • Engine overheating - Another aspect of your engine that is controlled by the belt is the water pump. The water pump is essential for cooling your engine, so when the serpentine belt wears down or becomes damaged, it can't activate the water pump as efficiently. This can lead to your engine overheating. An overheating engine is something that needs to be addressed immediately to avoid very expensive repairs.
  • Visible signs of wear - Of course, the most obvious sign that your serpentine belt is bad is that you can see visible signs of wear. If you see cracks, breakage, missing chunks, rib separation, abrasions, uneven wear, or other signs of damage on the belt, you need to replace it right away.
Worn Serpentine Belt

Image via Flickr by Bozart2000


How To Change Your Serpentine Belt

Safety First!

So you've determined that your serpentine belt needs to be changed. The first consideration, before you do anything else, is to be safe. Make sure that you have a clean, dry, and above all, flat and level place to work. This is to ensure that your car doesn't roll back while you're working on it. Block your wheels to keep the car in place while you work.

It's also a generally good idea to disconnect the battery before doing any work on the car. This can protect you from accidental shocks should you touch the wrong components.


Studying the Belt

Your next step involves getting a new belt and studying the way the existing one is routed through the engine. Never pull the old belt off before acquiring the new one. It's a good idea to get a routing diagram for the belt, and most cars have a routing placard under the hood. Usually, there is also a routing diagram in your owner's manual. Other than this, you may find a diagram on the internet, or in a repair guide for your vehicle.

It's important to have this diagram close by to avoid routing your belt incorrectly. There are a half-dozen pulleys around which it needs to wind, so it's not uncommon to install the belt incorrectly. After you've gotten the routing diagram, study the way the belt currently winds through the pulleys.

Check the way the belt fits into each one — some pulleys take the smooth side of the belt, while others take the grooved. A general rule of thumb is that a pulley with grooves on it takes the grooved side of the belt. Take notes if needed. When you think you've got a good handle on the routing, it's time to start changing out the belt.


Checking the Tension and Movement

First, locate the tensioner assembly. This is normally located on the front of the engine, between the crankshaft and the pulleys for the alternator. When you have located the assembly, check the tensioner arm, which should show a maximum of 1/32 inches of movement, with the belt running smoothly with no vibration. If the arm moves more than this or the belt vibrates, the tensioner is bad and may need to be replaced.

Next, using a serpentine belt tool, rotate the tensioner arm as far as you can and release it while feeling around for creaking and binding in either direction. Likewise, the pulley should move smoothly and freely with the spring maintaining an appropriate tension, with no friction in the pivot.

If either of these seems problematic, you may have to change out the tensioner or pulley before you can install a new belt. These parts are not very expensive, but in front-wheel-drive vehicles, you may need to have the engine supported before the tensioner can be removed because you'll need to remove the engine mounts to access the tensioner. This can be a complex process that requires help from a professional to accomplish.

If you can safely support the engine, or if you have a rear-wheel drive that doesn't require engine support, you can loosen the tensioner assembly with a socket wrench, fit the new assembly into place, and tighten it down once more.


Releasing the Tension

Since your belt is under tension, be very careful releasing it, as you don't want the belt to snap off, which could lead to injury. Using your serpentine belt tool, rotate the tensioner to loosen the belt, and slide the drive belt off of the pulley. Check the pulley for roughness and how smoothly it rotates. It should be smooth, and it should rotate easily without rumbling.

Keep the tension off while removing the old belt. When the belt is completely off, you can slowly release the tensioner. Again, be very careful as the tension can present a danger if it releases too suddenly.

Fitting the New Serpentine Belt

Using a belt placement tool to help with proper alignment, route the new belt around the path that you previously studied. Rotate the tensioner as you load the belt around the crankshaft pulley, around the grooved pulleys, and finally onto the non-grooved, rounded roller. Double and triple check to be sure that the belt is aligned and follows the proper routing, then slowly release the tensioner to tighten the belt once more.

Finally, double-check everything again to ensure that your belt follows the proper routing, and check the tension to be certain it has the proper movement and fit. When you are certain everything is installed correctly, give the car a road test to be sure everything is running as it should.

If you need parts for your serpentine belt replacement, We are here to help. Check out ourselection of belts for your make and model, and get in touch with us today to place your order or for answers to any questions you might have.