drive belt definition, functions, working,

Things you need to know about a drive belt

In an automotive engine, a drive belt 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 work. The belt is alternatively called an 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, and working principle, as well as symptoms of bad or failing drive belts. I’ll also explain the advantages and disadvantages of a drive belt.


What is a drive belt?

A drive belt or serpentine belt is a single, continuous belt used in automotive engines to rotate multiple peripheral devices in the engine. The belt is allowed to pass over more than 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 of 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 layouts, the backside of the belt, which is smooth is used to drive some devices. The design is typically limited to components with the need for less torque or where a large enclosed 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 belts 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 driven by the belt. So, the steering assist will be lost as the power steering pump is disabled from the drive.
  • The alternator that also supplies electrical power will stop working as the device is disabled.

other functions are mentioned according to the various types of drive belts out there.

A drive belt is a single component that controls various engine components which are earlier mentioned. Below is the diagram of the 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 a serpentine belt when an engine has one drive belt.

Types of drive belts

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

Serpentine belt:

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

Drive belts or V-belts:

These types of belts 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 of 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 a V-belt because of its tapered rubber teeth. One of the issues with these types of drive belts is the complexity and expense and they are trickier a bit to get to the right tension. The belt can rotate on the pulley under a hard load. An improper charge will occur to the alternator if the drive belt loses. It can also cause the car to overheat.

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 they can last throughout the engine’s lifespan. Instead of drive belts that crack or break over time.

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 to the drive belt. With the above-mentioned components the belt drives, the engine may not run at all, if it’s bad. As soon as 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 about a drive belt working:

Symptoms of a bad or failing drive belt

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

Broken drive belt:

A broken drive belt won’t be able to drive the engine components. This 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, or 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. It often occurs on the ribbed side. if such happens, the engine will make chirping or squeaking noises. The squeaking noise is one of the early signs of a worn-out drive belt, often happening 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 damaged. Drive belts are under tension to properly work, it had to be manually adjusted in 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 a wear sign or stick. It should be replaced along with the drive belt; it may take extra labor, 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 a drive belt used in an automotive engine:

  • Serpentine belts consume less space and are more 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.


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

  • The vehicle instantly loses 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.

Related Article:

In conclusion, we have examined in detail 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!


Leave a Reply

Your email address will not be published. Required fields are marked *