Serpentine Belt Vs. Timing Belt – What Are The Differences?

Serpentine Belt Vs. Timing Belt – What Are The Differences?

The smooth operation of your car depends on many factors. You don’t have to be aware of all the parts inside your ride, but it’s essential to at least know about a few of them. A car is comparable to the human body; it has various parts working together to function as a single cohesive unit.

Some are of greater importance than the rest because if they stop working, the entire system suffers. We will cover two critical parts of a car – the serpentine belt and the timing belt.

If you have an electric vehicle, you don’t have to worry, as they don’t require any belts to perform their operations. Instead, an electrical component operates the various parts present inside it.

A little bit of the History of Belts in a car:

In the early days, there used to be multiple belts inside the hood of the vehicle. Each of these belts used to power exactly a single part of the car.

Water pump, alternator, air conditioning, etcetera have separate belts for their operation. Having multiple belts came with some significant disadvantages.

A lot of space was required to accommodate these belts:

You might remember looking at the pictures of old cars and wondering why they have such a huge hood. One of the reasons was that it had multiple belts inside, spinning and operating exactly a single component. It required various pulleys for them to spin on.

The efficiency of the car took an enormous hit:

It is evident that operating multiple belts and multiple pulleys require more power. Thus the car from earlier years was not as efficient as modern vehicles.

The vehicles gave less mileage:

Apart from the classic car’s engine, they were not economical was multiple belts. The more power spent on spinning separate belts, the less the car’s mileage.

Mechanics had a tough time identifying the fault:

Imagine having to diagnose a squeaking sound coming from inside the hood. The mechanics spent lots of time inspecting each belt and the pulley it was attached to individually. Thus, the cost of maintenance of the car was extremely high.

It was expensive to replace all the belts:

If for some reason, all the belts required replacement, it would be a considerable burden on the owner of the car. He would have to shell out a massive amount of money on each of the belts.

Serpentine Belt:

It was necessary to find an alternative to the multiple belt system in the cars, due to its disadvantages. The serpentine belt was the answer to the problem of numerous belts.

In modern vehicles, if you open the hood, you will most likely find only one or sometimes up to three belts. You will find the serpentine belt on the side of your engine and is easily visible. The timing belt instead is covered and protected and cannot be seen.

The serpentine belt is one single belt that operates multiple peripherals of an engine. It always has multiple grooves on the inside. The serpentine belt most often requires the following components to function:

1. Pulleys:

Each of the devices that the serpentine belt will operate has a pulley that it wraps around. For example, the alternator, the power steering, and the air conditioning compressor. A single serpentine belt will wrap around the pulleys to operate the peripherals to which they connect.

2. Idler Pulley:

The job of this pulley is to guide and route the serpentine belt. It provides a rotating point to the belt and to loop around. The idler pulley gives the belt a curved shape due to which it is known as a serpentine belt. In modern cars, there’s only one idler pulley.

3. Belt Tensioner:

There are different types of belt tensioners present in the car, as the belts require proper tension to operate at maximum efficiency. These belt tensioners are either automatic or manual. There are two automatic variants, spring-loaded and hydraulic.

Advantages of Serpentine Belt:

Advantages Of Serpentine Belt

It has significant benefits compared to the old style of multiple belts. Here are a few of them:

1. Less Space Consumption:

A single belt to operate various peripherals means far less space requirement. It makes the life of the mechanic easier, as other components are easily accessible.

There is no need to remove multiple belts and pulleys to access something underneath.

2. Lower Maintenance Cost:

Instead of replacing multiple belts, you now have to replace a single one if any problem arises, thereby drastically decreasing the maintenance cost.

3. Good Mileage:

Reducing the number of belts lessens the load on the engine and the power requirements to operate. These factors lead to a far better mileage compared to the multiple belt system.

The disadvantage of Serpentine Belt:

There’s only one major disadvantage of the serpentine belt. Any fault in the belt and all of the devices it is attached to are affected. In the case of multiple belts, if any belt got damaged, only a single device operation suffered, and the car could still operate.

Will the car operate if the serpentine belt is damaged or broken?

If the serpentine belt breaks or somehow gets damaged, the car will not operate. It will still be drivable, but you will end up causing significant damage. As the belt is attached to the water pump, in the case of breakage, the water supply will stop, and the engine will begin to overheat.

It will also prevent the functioning of the alternator, which is responsible for charging the car’s battery. Without a charged battery, you will have to push start your vehicle.

You also don’t want a broken belt running wild inside the hood. A ripped belt can damage coolant hoses and also the shrouds of the radiator.

Therefore, it is recommended to get the serpentine belt fixed as soon as possible in case of any damage.

Symptoms of a damaged or broken serpentine belt:

If the serpentine belt breaks or damages, you will hear loud slapping noises. You might also hear squealing or knocking sounds coming from the hood of your car.

Other symptoms include the car heating up. If you find no issues in other components that might cause the engine to heat up, then a broken serpentine belt is responsible.

If you see a battery sign light up in the information cluster of your car, it could indicate that the alternator is not functioning. The most likely reason for an alternator to not working is a worn out or broken serpentine belt.

Causes of the damaged serpentine belt:

Numerous reasons can cause the serpentine belt to break and require immediate replacement. These could be the following:

1. Regular depreciation:

Usually, the serpentine belt has a long life span. It can work perfectly fine for sixty thousand to a hundred thousand miles. Sometimes the manufacturers themselves list when the belt should be inspected and replaced.

Inspecting the belt is quite easy and can be done at home. It doesn’t require any tools. Just open the hood, locate the belt, and check the inner side, which has the grooves. There shouldn’t be any cracks in them, and if you find any, it means that the belt needs replacement. The rubber of the serpentine belt gets hard with use and begins to crack. It also begins to lose tension as it stretches with regular wear and can cause the belt to slip.

Depending on the manufacturer, replacing the belt could be an easy task and done at home if you have skill and experience. Sometimes the manufacturers provide the instruction in the owner’s manual of the vehicle.

You can also find the replacement instructions for your car make and model on YouTube. If you don’t have much experience, it is best to get a mechanic. It is a simple job for them and won’t cost much.

2. Problems with Belt Tensioners:

There is either an automatic or manual belt tensioner in cars. Modern vehicles always go with the automatic variant, and they are of two types: spring-loaded and hydraulic.

A spring-loaded belt tensioner can become weak with use and unable to generate enough tension. Proper tension is essential for the serpentine belt to operate without problems. If it weakens, the belt begins to slip and cause issues. The serpentine belt will also be worn out faster, and it can break or damage. You will be able to identify a loose belt by loud squealing noises coming from under the hood.

A hydraulic belt tensioner uses a shock absorber to achieve the tension required to operate at maximum efficiency. It can also damage due to wear and leak. You can identify the issue with it by hearing rattling sounds from the serpentine belt area.

The solution in case of automatic belt tensioners getting damaged is to replace them. They are not expensive, and they cost around twenty to seventy-five dollars. Replacing them requires skill and experience, so you should leave it to the mechanics.

The manual variant of the belt tensioner, as the name suggests, requires the tension to be manually adjusted. The serpentine belt begins to stretch over time, and thus the tension needs to be modified in time. If you do not take care of it in time, the belt will begin to slip and break or damage and require replacement.

3. Problem with Idler pulley:

The idler pulley helps in the routing of the serpentine belt. It doesn’t generate electrical or mechanical power. The idler pulley spins on a bearing, and with regular use, this bearing can get damaged. It can cause either whirring or screeching noises to come from under the hood.

As other parts can produce the same sounds in case of a problem, it can be challenging to identify the problem with idler pulley bearing. The mechanic will have to check and find the source of the noise thoroughly.

Fixing the idler pulley problem is a simple replacement, as it is cheap and readily available. The labor cost will depend on the time it took for the mechanic to identify the issue.

4. Damage caused by oil leakage:

Sometimes the engine oil can leak and drop on the serpentine belt damaging it in the process. The engine coolant can also leak to the belt and damage it.

It is essential to identify and fix the leakage before replacing the serpentine belt. If you do not resolve the leakage issue and put on a new belt, it might damage within a week and end up wasting your money.

5. A Misaligned Pulley:

As the serpentine belt operates various components by running on their pulleys. If any of these devices get misaligned, they can cause damage to the serpentine belt. Usually, a misaligned pulley will cause one side of the belt to get a tear.

It is possible to observe this misalignment by eye. The mechanic will be able to find and adjust the alignment accordingly and replace the belt if damaged.

Serpentine Belt inspection and replacement:

As mentioned previously, the serpentine belt has a long life span. It won’t damage under normal circumstances. Therefore, look out for all the symptoms listed above and take immediate action. You can also visually check the belt for cracks now and then once you rack up over 60,000 miles on your car.

The belt itself is not expensive and will cost around 35 to 70 dollars, depending on your vehicle’s make and model. Only replace it yourself if you have experience and skill. Otherwise, it is better to get a mechanic to replace them. The labor cost will be less than 150 dollars and won’t take much of your time.

Timing Belt:

It is one of the essential belts in the car engine. Unlike the serpentine belt, it is not possible to inspect the timing belt with naked eyes quickly. The timing belt is covered and hidden behind protection.

The function of the timing belt:

The timing belt is a toothed belt that synchronizes the crankshaft movement and camshaft of the engine. If the movement of these components is not synchronized, it can also cause a severe accident. Moreover, let’s discuss the function of the camshaft and crankshaft briefly as they are a significant part of an internal combustion engine.


The crankshaft is present in the lower block of the internal combustion engine. The piston rods attach to the crankshaft, and the pistons connect to the rods. The crankshaft is the principal rotating part of an engine. As the crankshaft rotates, it causes each of the pistons to move up and down.


The camshaft is located at the top of the crankshaft. It connects the crankshaft through a timing belt. The camshaft has an inlet and exhaust valve, and it also has a fuel pump cam.

As the crankshaft rotates, it causes these valves to open and close at precise timings in sync with the pistons’ movement.

A complete cycle of and internal combustion engine has four steps in one entire cycle:

1. Intake:

In this process, the piston moves down and causes the camshaft to open the inlet valves to draw in the air and fuel mixture.

2. Compression:

In this step of the cycle, the inlet valve is closed, and the piston begins to move up and thereby compress the fuel and air mixture.

3. Combustion:

Just as the piston gets to the peak of its compression stroke, the spark plug emits a spark. It combusts the fuel-air mixture. This combustion causes the piston to move down, and hence the engine gains power.

4. Exhaust:

The exhaust valve opens, and the piston travels back up. Once the piston moves up, it causes the exhaust gases to move out of the open valve. As the valve reaches the top, the exhaust valve closes.

This process then goes on continuously in the internal combustion engine when it’s running. The engine has multiple cylinders starting from two and going up to twelve. The process mentioned above is of a single one, and this cycle is going on in each of them.

Now that you know the mechanism of the internal combustion engine and understand the function of crankshaft and camshaft, you will realize the importance of the timing belt. It is the function of the timing belt to move both the shafts at precise timings. The timing belt is responsible for the perfect opening and closing times of the valves in the camshaft.

Timing Belt Tensioners:

Just like the serpentine belt, the timing belts also needs to operate under a precise tension. Almost all the latest models have an automatic tension adjuster for the timing belt. Older models have a manual adjuster to adjust the certain tension required by the timing belt.

Timing Belt Failure:

The timing belt usually falters when its tooth damages or wears off. It can cause the timing belt to slip from the cogs that are spinning, thus disrupting the synchronization of the crankshaft and camshaft.

If the timing belt breaks, it will lead the engine to no longer work. It can be catastrophic if the timing belt breaks while the car is in motion. The timing of the shafts would be off, and the valves that are supposed to be close at a specific time in the cycle would be open. It would bend or break the valves, and it might also destroy the engine block.

Timing belt replacement and maintenance:

Manufacturers always list the exact mileage upon which to replace the timing belt. Most cars require a replacement at 30,000 miles. A good quality timing belt can last up to 100,000 miles.

It is of uttermost importance to replace the timing belt according to the manufacturers’ recommendation. I would even recommend changing it earlier if possible, as timely prevention could prevent a disaster in the future. If you purchase a second-hand car, replace the timing belt as soon as possible, even if below the recommended mileage.

Replacing a timing belt requires extra care, as all the things that are in sync with the crankshaft, especially the camshaft, must be appropriately timed. It is necessary to follow the timings mentioned in the owner’s manual of the car. The cost of replacing a timing belt can go up to seven hundred dollars, depending on the make and model of your vehicle.

Timing Belt versus Timing Chain:

Most newer vehicles are opting for timing chains instead of a belt. In the beginning, timing chains were standard in the cars. Later the manufacturers shifted to timing belts as they are easier to maintain and manufacture. It was also more beneficial for the company as timing belts wear off fast and need replacements.

Most owners end up selling their cars for this reason alone and buy newer cars. Thus the manufacturers end up making more profit.

Timing chains are more durable if you compare them to timing belts and can run up to 300,000 miles. However, they do require some extra parts to run and also requires oil to operate smoothly. The engine oil acts as the lubricant for the timing chains. Therefore, if your engine oil remains full, you won’t have to worry about the timing chains. Thus, the timing chain will be preferable for a neglectful person.

Serpentine Belt versus Timing Belts:

In conclusion, the difference between both of these essential belts of a car should be easily understandable for you now. They both perform important tasks under the hood of your vehicle and make sure that it operates without any hiccups.

The serpentine belt is more accessible, and you can visually inspect it. The timing belt is hidden, and you will require tools to access it and visually inspect it.