What Is Serpentine Belt in Car?

What Is Serpentine Belt in Car

A serpentine belt is an important part of your vehicle’s engine block, but do you know what a serpentine belt really is? And what does a serpentine belt do? Where is the serpentine belt? Put simply, A serpentine belt delivers power to vital systems in your car like your alternator, A/C compressor, and others.

In some cases, it also supplies power to your water pump. It’s a long, winding rubber band of sorts that is attached to your crank pulley. Starting from there, it makes its way around your engine block, delivering power to all of the aforementioned vehicle systems.

What Does A Serpentine Belt Do?

A serpentine belt, or drive belt, is a long rubber belt that carries power to the multiple peripheral devices in an automobile engine, such as an alternator, power steering pump, water pump, air conditioning compressor, air pump, etc. The belt may also be guided by an idler pulley and/or a belt tensioner which may be spring-loaded, hydraulic, or manual.

The serpentine belt uses pulleys and a belt tensioner to transfer power from the engine crankshaft to all other components.

To allow the belt to travel over more than three pulleys with a sufficiently large wrap angle to avoid slippage, idler pulleys are included that press against the back of the belt, forcing the belt into a serpentine shape.

To accommodate this bi-directional flex while remaining strong enough to transmit the total force required by multiple loads, a serpentine belt is almost always a multi-groove (Multi-V, Poly-V, or Multi-Rib) construction.

What is a belt tensioner?

Most cars today have a self-tensioning device called a belt tensioner or an automatic belt tensioner. This device keeps the serpentine belt at the right amount of tension for it to run properly. Most belt tensioners have an internal spring and pulley to apply the right amount of force to keep the serpentine belt tight and prevent it from slipping, squeaking, or overheating.

Where Can I Find the Serpentine Belt Diagram for My Car?

Often the hardest part of replacing a serpentine belt is making sure the new belt is properly routed around the engine’s pulleys. Vehicle manufacturers create serpentine belt diagrams that are designed to aid with this task.

Serpentine Belt Diagram

On some vehicles, the serpentine belt diagram is located on a sticker somewhere in the engine compartment. However, if your car doesn’t have a sticker, you can easily look up the diagram in a repair manual or repair database.

Another option is to take a picture of the old belt before removing it. You can refer to the picture when installing the new belt to ensure correct routing.

What happens if the serpentine belt breaks while driving?

If your serpentine belt is worn, damaged, contaminated, or breaks, engine accessories will not be able to rotate at the correct speed, resulting in reduced electrical system performance. This can result in a sudden loss of power assistance to the steering system, causing the steering wheel to suddenly become very difficult to turn.

A broken serpentine belt can prevent the water pump from circulating coolant through the cooling system, causing the engine to overheat. And it can cause the alternator to stop producing power to run the vehicle’s electrical/electronic systems and charge the battery – the headlights dim, the radio doesn’t work and the battery will die.

Can you drive a car if the serpentine belt breaks?

If you are wondering whether or not you can drive your car without a serpentine belt, the answer is clearly negative. There is absolutely no way you can drive a vehicle without a serpentine belt, as the serpentine belt performs the important function of supplying antifreeze to vital parts of the engine.

The serpentine belt drives the water pump, and without it, coolant flow is insufficient to maintain engine temperature. It is also important to consider that the serpentine belt drives the power steering pump. Without the serpentine belt, the power steering pump that supplies the hydraulic pressure will stop working. As a result, it becomes difficult, if not impossible, to turn the steering wheel. 

What are the signs of a failing serpentine belt?

If your serpentine belt is failing, you may notice performance issues with your vehicle. The vehicle may frequently overheat. Your air conditioning or power steering may fail to work or not work properly. You may notice your vehicle battery failing to recharge if the alternator is affected by a bad serpentine belt.

Additional signs of a possibly bad serpentine belt include:

  • Flickering lights on start up
  • Failure to start
  • Dimmed headlights
  • Continuously illuminated amperage light

Your car can often stall while driving if the serpentine belt is not doing its job. If the belt breaks while driving, the battery will eventually die, and the belt could cause other damage if it flaps around under the hood.

How much does it usually cost to replace a serpentine belt?

But, what does a serpentine belt replacement cost? The cost of the serpentine belt itself could be around $50 and the cost of labor could be around $150. As a result, a serpentine belt cost for replacement could range from $70 to $200 depending on your exact model and where you get it.

You can cut the cost of replacing a serpentine belt in half by doing this job yourself! Your exact replacement cost is dependent on the type of vehicle you own, but most of the price of this job is in the labor.

Keep in mind: Just about all engine drive belts are different, so make sure you have all of the proper information on hand when ordering a new belt. When in doubt, always refer to your owner’s manual.

How often should the serpentine belt be replaced?

Your serpentine belt was made to last. Under ideal circumstances, your car’s serpentine belt should last 60,000–100,000 miles. It’s important to replace this belt as part of your vehicle’s scheduled maintenance (even if it looks okay) to avoid it breaking while you’re on the road.

It usually takes approximately thirty minutes for a mechanic to replace a serpentine belt. With the right tools and equipment, an auto mechanic can complete the process within thirty minutes to an hour.


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