Home CAR GUIDE How to Check Car Serpentine Belt

How to Check Car Serpentine Belt

serpentine belt is a single, continuous belt which is used to drive multiple peripheral devices in an automotive engine, such as an alternator, power steering pump, water pump, air conditioning compressor, air pump, etc. The belt might also be guided by an idler pulley and/or a belt tensioner (which may be spring-loaded, hydraulic, or manual). Serpentine belts are common in the latest vehicles and are essentially the standard for the modern vehicle.

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A car engine’s serpentine belt also called as an accessories belt or drive belt, powers individual systems external to the vehicle’s engine, such as the compressor, air conditioner, alternator, and other systems. Some cars utilize more than one serpentine belt for this purpose, dividing the driving task among two or more belts. The important functions performed by the serpentine belt help to make it an essential part of the engine system, making regular inspection and maintenance of the belt a crucial step in keeping the car operational.

The functions of Serpentine Belt are as follows-


The serpentine belt plays an important role in a car’s electrical charging system. It is attached to pulleys on the car’s alternator in order to provide power to this unit, which in turn delivers electricity to the car’s battery so it can build and hold an electrical charge. In this capacity, the serpentine belt replaces individual “V” belts that serve an alternator or other components exclusively as a single belt means simpler replacement and fewer parts that can fail.


The serpentine belt powers several mechanical components of a car. The power steering system, for instance, is dependent upon the power delivered to it by the serpentine belt. The car’s cooling system also consists of several components powered by the serpentine belt, which includes the water pump, radiator fan, and air conditioner compressor.


The serpentine belt can only fulfill its purpose if it is held under the correct tension. A mechanical device called a tensioner applies just the right amount of tension to the belt for keeping the belt running at the proper speed and resistance to perform its functions. A loose serpentine belt will slip, which will result in reduced efficiency and, in some cases, an annoying whistling noise that signals the need for a replacement belt. Some older cars need manual tensioner adjustment, while modern cars have tensioners that adjust themselves automatically.


The serpentine belt provides many of the basic functions that a car needs to operate. A car simply cannot run without the help of a working serpentine belt. If the belt breaks or works itself off during the operation, the car will immediately lose its ability to cool the engine, charge the battery, and engage the automatic steering or to run the air conditioner.


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Keeping the serpentine belt system in optimum condition can make sure that the belt continues to perform its vital role in the car’s operation. Hard-to-spot weaknesses can creep into the belts with natural wear or exposure to engine fluids. Most serpentine belts can give a reliable performance at 50,000 to 60,000 miles’, but changing the belt at around this interval will help car owners to avoid eventual belt failure and resulting in a car breakdown. The pulleys and tensioner also need to perform within specifications to ensure a longer belt life.

Video of How Serpentine Belt Works

Symptoms of a Bad or Failing Serpentine/Drive Belt

1. Squealing noise from the front of the vehicle

If you notice a squealing noise that is coming from the front of your vehicle, it could be coming from the serpentine belt. This could be because of slippage or misalignment.

2. Power steering and AC not working

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If the serpentine belt completely fails as well as breaks, then your car will break down. In addition, you will see the loss of power steering, the air conditioning will not be working, and the engine will no longer be cooling like it used to be. If the power steering fails when the vehicle is moving it could lead to serious safety issues. Preventative maintenance is one way to ensure your belt does not break while you are driving.

3. Engine overheating

Since the serpentine belt helps to provide power to cool the engine, a failing belt can cause your engine to overheat as the water pump will not turn. As soon as your engine starts overheating, just have it inspected by a mechanic because it can lead to a breakdown and cause damage to your engine if it is left to keep overheating.

4. Cracks and wear on the belt

It is a good idea to physically inspect your serpentine belt regularly. Check for cracks, chunks missing, abrasions, rib separation, uneven rib wear, as well as damaged ribs. If you notice any of these, it is time to change your serpentine/drive belt.

How to Replace a Serpentine Belt

Step 1

Take a good look at your repair manual as well as your belt routing diagram under the hood before beginning. If you need to, you can go online and find the belt routing schematic.

Step 2

Just look at the way the old belt wraps around the pulleys. Take the new belt in hand and practice to match the routing.

Step 3

•    Find the self-adjusting tensioner and know that you need to be careful when releasing tension from the belt. The back side of the belt runs against the tensioner, so it will appear more like a smooth roller than a pulley.

•    Position the wrench or special removal tool on the tensioner and make sure you have room to remove the tool once the tensioner is released.

•    Release the tension and you’ll notice that the tensioner tool is a flat bar rather than a ratchet. This will help you get into the tight clearance for the tensioner’s roller.

•    This will help you get into the tight clearance for the tensioner’s roller.

Step 4

•    Remove the old belt and check the tensioner pulley for any wear by using your hand to spin it before installing the new belt. Noisy, loose or overly tight tensioner pulleys will have to be replaced. Also, check all pumps and idler pulleys to ensure they move freely too.

•    Check the idler pulleys as well as the pulleys for the water pump, alternator, smog pump, A/C compressor and any other accessories for wobble or deflection.

Step 5

•    Install the new belt and line up all belt ribs in the pulley grooves. Make sure that the belt is not twisted.

Step 6

In the end, just tighten the tensioner in the end.

Video of How to Replace a Serpentine Belt in Your Car

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