Things you need to know about a drive belt

In an automotive engine, a drive belt which also known as a serpentine belt is used to drive various engine components. These components might include a power steering pump, alternator, water pump, air conditioning compressor, etc. The belt is often placed on an idler pulley which serves as a guide or a belt tensioner. This is either spring-loaded, hydraulic or manual.

A serpentine belt is positioned at the outer part of the engine which provides power and drives to the engine devices making the vehicle to work. The belt is alternatively called alternator belt, accessory drive belt, or fan belt.

drive belt definition, functions, working,

Today we’ll be looking at the definition, function, components, diagram, types, working principle, as well as symptoms of bad or failing drive belt. I’ll also explain the advantages and disadvantages of a drive belt.

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What is a drive belt?

A drive belt or serpentine belt is a single, continuous belt used automotive engines to rotate multiple peripheral devices in the engine. The belt is allowed to pass over more three pulleys which are designed to fitly enclose the belt to avoid slipping. Idler pulleys are pressed against the back of the belt, forcing it into the shape in the pulley.

A drive belt can last at least more than 10,000 miles. Cranks or breaks can easily be detected as they can see on the side in front-wheel drive vehicles. in rear-wheel drive vehicles or cars with boxer engines, it’s visible from the front. In some rear-wheel cars and older cars, the drive belt also drives the front engine fan. some engine design uses two of them depending on the configuration and the device layout.

In some engine layout, the backside of the belt, which is smooth is used to drive some device. The design is typically limited to components with the need for less torque or where a large enclose angle is present.

Functions of a drive belt

Below are the functions of a drive belt in an automotive engine:

  • The primary purpose of a drive belt is to drive or power the engine accessories.
  • Drive belt use one source of energy to power multiple components
  • It increases the mechanical efficiency of the engine.
  • Since the engine water pump is powered by a drive belt, it will stop running and cause overheating if it breaks.
  • Also, the hydraulic power steering is drive by the belt. So, steering assist will be lost as the power steering pump is disabled form the drive.
  • The alternator that also supplies electrical power will stop working as the device is disabled.

other functions are mentioned according to their various types of drive belt out there.

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A drive belt is a single component that controls various engine components which are earlier mentioned. Below is the diagram of components a drive belt powers:

drive belt

drive belt components

The belt is driven by a pulley attached to the engine crankshaft. Most vehicles are designed to use one or two drive belts, but it’s called serpentine belt when an engine has one drive belt.

Types of drive belts

Below are various types of drive belt used in an automotive engine:

Serpentine belt:

The serpentine types of the belt are the most common belt used today. It’s a single belt used to power most essential components of the vehicle and it is easy to change. A socket is used to pull the tensioner pulley in order to remove the belt.

Since a serpentine belt is single belt use to drive multiple devices, the car owner is assured to be on the roadside if it got broken. This is why regular inspection should be made of these types of drive belt to avoid the future issue. But a quality serpentine belt will surely serve at least 90,000 miles.

Drive belt or V-belts:

These types of the belt are often found in older vehicles, but they offer several advantages. Apart from the crank pulley, the belt power at least one or two devices depending on the engine design. There are several individual belts to drive the power steering, air conditioning compressor, alternators, water pump, and radiator fan.

If one the belt break, the driver is likely to get home unlike the serpentine belt that powers all components with a single belt. But depends on the belt is driving. A drive belt is called v-belt because of its tapered rubber teeth. One of the issue with these types of the drive belt is the complexity, expense and they are trickier a bit to get to the right tension. The belt can rotate on the pulley under hard load. An improper charge will occur to the alternator if the drive belt lose. It can also cause the car to overheat.

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Timing belts:

Timing belts are types of drive that connect the crankshaft and camshaft, keeping them in sync. The belt is located behind the timing cover, one does likely not see it. The belt is important in the automotive engine as the combustion process relies on it. it can work for at least 60,000 to 90,000 miles before replacement. Well, some engines are designed with timing chains instead of belts so it can last throughout the engine lifespan. Instead of drive belts that crack or break over time.

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Working Principle

The working of a drive can be simple and complex depending on the engine design. The belt work with the idler, tensioner, and pulleys to keep the devices connected the drive belt. With above-mentioned components the belt drives, the engine may not run at all, if it’s bad. As soon the engine is running, the serpentine belt continues to operate until the vehicle is shut down. The power used to control the crankshaft that serves as the primary source of energy is obtained from the combustion process.

Watch the video to learn more on a drive belt working:

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Symptoms of a bad or failing drive belt

Below are the signs or symptoms of bad and failing drive belt:

Broken drive belt:

A broken drive belt won’t be able to drive the engine components. The will cause malfunctioning of the component it powers. Consider changing as soon as the problem is noticed else it will cause damage to the engine devices. A DIYer will be able to change the serpentine belt, but for the v-belt, a professional mechanic should fix it.

Normally, whenever general maintenance is performed, the drive needs to be inspected. The mechanic will ensure the belt does not contain cracks, missing chunks and signs of wear.

Cracks on the drive belt and missing chunks:

There is no other option but a replacement, if there is a missing chunk on a drive belt. If often occur on the ribbed side. if such happens, the engine will make chirping or squeaking noises. The squeaking noise is one of the early sign of a worn-out drive belt, often happen in the rainy season.

Leaking oil in a drive belt:

If the drive belt is saturated in oil, the oil leak will be the first thing to get fixed, else the new belt will also be damage. Drive belts are under tension to properly work, it had to be manually adjusted in the regular interval on older cars. If the belt is loose by this symptom, the driver will experience a screeching noise that won’t last long after the engine starts.

Automatic spring-loaded drive belt tensioner:

The spring-loaded drive belt tensioner could show wear sign or stick. It should be replaced along with the drive belt; it may take extra labour, but that will be a better option while trying to save the components. this will also avoid the oil from leaking.

Advantages and Disadvantages of a Serpentine Belt


Below are the benefits of drive belt used in an automotive engine:

  • Serpentine belts consume less space and are effective than the older multiple drive belt system.
  • The belt is able to undergo an increase in tension without stretching.
  • Since higher tension reduces slip, belt life and mechanical efficiency are increased.
  • The belt is much easier to maintain and replace since there is no need for multiple belts to be removed.
  • Since only one tensioner belt is needed for all the peripheral components, they can simply be mounted on the engine without the need to swivel.
  • Less slip allows a serpentine belt to work well on lower-ratio pulleys as the engine load is reduced.
  • Fuel economy and available power are increased.
  • The tendency of flip over in the pulley groove is eliminated.

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Despite the great advantages of a serpentine belt, some limitation still occurs. Below are the disadvantages of the drive belt:

  • The vehicle instantly looses multiple critical functions as so as the belt breaks or is knocked loose.
  • The vehicle becomes unusable in no time as the engine cooling is terminated.
  • Lack of redundancy.
  • Breakage of the single belt means loss of all accessories.

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In conclusion, we have examined in details on a drive belt, its definition, functions, types, working, and advantages and disadvantages were explained.

I hope you enjoyed the reading, if so, kindly comment, share and recommend this site to other technical students. Thanks!

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