An engine belt, also known as the serpentine belt or “drive belt,” is a pretty important component of your car… but what does the engine belt do? 

It has one job… Transferring the rotational power from the crankshaft to the pulley-driven accessories on your vehicle, these include…

  • The Power Steering pump
  • The A/C compressor (for climate control)
  • The Alternator is powered by the car’s serpentine belt.
  • The Waterpump

As you can probably tell these are some important components that need to work for you to drive safely. 

Without the engine belt, these components don’t function, leading to all kinds of trouble, including engine overheating and loss of steering assist.

In this article, we will cover engine belts, what they do, and the different types.

 

Types of Engine Belts

There are different types of engine belts used by manufacturers, but the two most common ones are the V-belt and the ribbed belt… ie a “serpentine belt.”

The V-belt is named after its shape, which resembles the letter “V”. It is made of rubber and has a narrower cross-section at the top and wider at the bottom. This allows the belt to “sit” inside of each half of a drive pulley.

“V” Style engine belts - jerrypetrillo.com
“V” Style engine belts – jerrypetrillo.com

The V-belt is commonly used in older vehicles and is known for its durability and reliability.

These are “old school.” The belt tensioner is adjusted by a mechanic to set the belt at the correct tension. The drawback of this is as the belt stretches and wears it will loosen up and need re-tensioning. 

The ribbed belt, also known as the multi-ribbed belt or serpentine belt, is a newer and more advanced type of engine belt. These use hydraulic or spring-loaded tensioners that automatically adjust as the belt wears down, making them super reliable.

A picture of a serpentine engine belt - jerrypetrillo.com
A picture of a serpentine engine belt – jerrypetrillo.com

Serpentine belts have multiple longitudinal ribs on their inner surface. 

These ribs allow for better grip and increased surface area, resulting in more efficiency. The ribbed belt is used in modern vehicles due to its superior performance and longer lifespan.

There is another type of engine belt that will make any mechanic’s blood boil, it’s known as a stretch belt. These are serpentine belts that DO NOT use a tensioner whatsoever. They are spun onto pulleys using special tools, once these are installed they use their elasticity to stay at the correct tension. 

These belts can be a nightmare to get on without tearing~…

I personally hate them 🙁

Advantages of Serpentine Belts

The ribbed belt, often referred to as the car’s serpentine belt, differs from the V-belt in its structure and design. While the V-belt has a single groove on its inner surface, the ribbed belt has multiple ribs that run along its length. 

A huge advantage of using a ribbed belt is its ability to drive multiple components simultaneously. With a single ribbed belt, you can spin multiple accessories, such as the alternator, power steering pump, water pump, and air conditioning compressor all at once, using only ONE belt.

This eliminates the need for multiple belts and tensioners, making them more compact and efficient.

What does the engine belt do?

The engine belt works by transferring power from the engine to other components of the car. When the engine is running, it rotates the crankshaft pulley. The crankshaft is equipped with a pulley designed to accept the engine belt.

A close up serpentine belt - jerrypetrillo.com
A close-up serpentine belt – jerrypetrillo.com

As the crankshaft pulley rotates, it drives the engine belt along with all of the accessories it’s connected to.

By using different pulley size ratios car manufacturers spin all of the accessories needed to power various systems at just the right speed.

For example, an alternator has a very small pulley when compared to a power steering pump, this is because an alternator needs to spin much faster to generate the amperage needed to recharge your battery while driving.

Along with pumps and compressors, the belt also spins tensioner and idler pulleys. These play a crucial role in maintaining the tension and alignment of the engine belt. 

The tensioner pulley is designed to keep the engine belt tight, ensuring proper power transmission and preventing slippage. On the other hand, the idler pulleys help guide the engine belt along its path and maintain its alignment with the pulleys.

Sometimes an idler is just needed to change the belt’s direction or make room for another component. 

The Importance of the Engine Belt

As we talked about earlier, the engine belt is a vital component of a car’s operation. It drives the systems your car needs to function properly.

The power steering pump relies on the engine belt to provide hydraulic pressure, allowing for easy steering. The water pump ensures that the engine stays cool by circulating coolant throughout the system. Lastly, the air conditioning compressor requires power from the engine belt to provide cool air inside the car.

Signs of Wear on the Engine Belt

The engine belt is a consumable item, over time it becomes damaged due to constant use and exposure to heat and friction.

It’s important to know the signs screaming “I’m about to break!” 

Common signs of wear on the engine belt include squealing or chirping noises, especially when starting the car or using the air conditioning. The squealing indicates slippage and should always be addressed ASAP.

Another sign is visible cracks or fraying on the surface of the belt. A great way to check this is to find a spot where the engine belt wraps around a pulley with the ribbed section exposed. Check for any signs a belt replacement may be necessary.

If you see cracking along the ribs where the belt is flexed back it’s time for a new one. This is the most common reason engine belts are replaced by far. 

If the engine belt appears loose or is slipping off the pulleys, it may need to be replaced. Some cars, especially BMW have tensioners that begin to fail and allow the belt to walk off of the pulley.

The best part? After the belt blows off the crankshaft pulley sucks it in, past the front seal, where it continues to blow up the engine by locking up the crankshaft. 

Use common sense, if the car’s systems, such as the power steering or air conditioning, are not functioning properly, or the screeching of your car in the morning can be heard far and wide, it could be a result of a worn-out engine belt.

Get it looked at ASAP to avoid damage that a misaligned or worn serpentine belt may cause! 

Maintenance of the Engine Belt

Proper maintenance of the engine belt is essential to prolong its lifespan and ensure optimal performance. Regular inspections should be conducted to check for signs of wear or damage. 

Be sure to inspect all pulleys and tensioners as well for damage or “cocking.” This indicates a possible failing bearing and shouldn’t be ignored…. Say hi BMW 🙂

Replacing the Engine Belt

If the engine belt shows signs of wear or damage, it’s time to head to the parts store for a belt replacement. 

step-by-step guide to replacing a engine belt

  1. Locate the tensioner pulley and use a wrench or socket to release the tension on the belt.
    2. Slide the old belt off the pulleys and remove it from the engine.
    3. Compare the old belt with the new one to ensure they are of the same size and type.
    4. Install the new belt onto the pulleys, following the correct routing diagram provided by the manufacturer.
    5. Use a wrench or socket to apply tension on the tensioner pulley and slide the new belt onto it.
    6. Double-check that the new belt is properly aligned with all the pulleys.
    7. Start the engine and check for any unusual noises or vibrations.

Keep in mind that this is a VERY generic guide, all cars are different. Always check the manual for your car or see a professional mechanic.

Don’t forget to spin every pulley the belt does while the belt is off to check for other component issues before installing a new belt. 

Common Problems with the Engine Belt

Several common problems can occur with the engine belt, slipping, squeaking, or misalignment. If the engine belt is slowly walking off the pulleys, it may be due to a loose tensioner or worn-out pulleys. In this case, the tensioner or pulleys may need to be replaced.

Probably the most common issue is a lack of tension or a worn-out belt will cause squeaking noises, mainly first thing after starting the car cold.

This happens because the loose belt has far less grip on the pulleys when cold. After slipping enough to heat the rubber it begins to gain traction and the noise stops. 

Far too many people think they “fixed it” as they rev the engine until the screech stops. Adjusting the tensioner or replacing the belt will resolve this issue. Check the alignment of the belt regularly and adjust it if necessary.

Wrapping Up Engine Belts

Your engine belt, or the car’s serpentine belt, is a vital component of your car’s operation. It enables various systems to function properly.

With its advanced design and improved power transmission efficiency, the ribbed belt has become the preferred choice in modern vehicles. However, don’t forget the tried and true V belt, a true workhorse. 

Regular maintenance and prompt replacement of an excessively worn engine belt are essential to avoid costly repairs and ensure safety on the road. By now I’m sure you understand the importance of the engine belt and how much that little strip of rubber makes possible in your car. 

Be sure to take a look under your hood and see how your belts are doing as part of your routine car care.

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