What is a Serpentine Belt? Here’s What You Should Know

Cars are a modern-day engineering marvel, but most of the magic is invisible to you as the driver. You simply turn on the car, hit the gas, and drive at your leisure and convenience. But behind the scenes, there’s a particular car part that provides energy to various vital car functions like engine cooling, power steering, and more and that is the serpentine belt. In this guide, we’ll cover what it does, how it works, and when is a good time for serpentine belt replacement.

All You Need to Know About Your Car’s Serpentine Belt | Metromile

What is a serpentine belt and what does it do? 

A serpentine belt is a snake-like belt (hence, the name) made of rubber that is part of your car’s engine and provides power to several parts of your car. These parts include:

  • The alternator
  • Air conditioner 
  • Power steering 
  • Water pump

The belt is located on the exterior of the engine and works with a closed-loop system. The serpentine belt connects various pulleys to transport energy sources that activate the aforementioned car parts. As your car runs, the belt consistently moves and powers other car parts seamlessly. 

What’s the difference between the serpentine belt vs. timing belt? 

Everyone has varying levels of car parts knowledge, ranging from “I don’t know a thing about car parts, I just drive” to “I’m an expert and can fix my own car” and everything in between. 

Regardless of where you’re at on the car knowledge spectrum, it can be easy to confuse the serpentine belt and timing belt. These car parts both have the word “belt” in them, but in fact, they serve very different purposes and are in different locations. 

As noted above, the serpentine belt provides power to other essential car parts and is on the exterior of the engine. 

A timing belt works to connect the engine valves of your car with the crankshaft so that the exhaust valves and the vehicle’s engine intake open and close seamlessly and in sync. The timing belt is located in the interior of the engine. 

An easy way to tell them apart is based on the types of grooves they have. Serpentine belts have vertical grooves, whereas timing belts have horizontal grooves. 

Though there are some major differences between serpentine belt vs. timing belt, oftentimes they both need to be replaced around the same timeframe, which is typically around the 60,000 to 100,000 miles mark. 

Keeping your serpentine belt in good shape 

Seeing as your serpentine belt powers so many other vital car functions, you want to do what you can to check in on the belt and make sure it’s in good shape (and keep it that way). 

The first thing you can do is consult your car’s owner manual to see how often you should check the serpentine belt. You can examine it yourself and see if there are common signs of wear and tear. For example, if you see cracks in the belt or see oil on it, it’s likely time for a repair. 

You may also be able to purchase a special gauge tool that can help you assess if there is damage that you may not be able to see. 

When should you get a serpentine belt replacement?

You should get a serpentine belt replacement every 60,000 to 100,000 miles or so. If you’re unsure if it’s ever been replaced, you may want to get it inspected by a professional or look for telltale signs that there is damage. According to The Drive’s Guide on Serpentine Belts, you should look out for the following: 


  • Fraying 
  • Cracking
  • Shiny or glazed surface area
  • Dirt or grease build-up
  • Slack


  • Squeaking, chirping squealing, or rattling noises (the most common)
  • Failing charging system or weak battery
  • Failing air conditioning
  • Overheating

You can also see if your engine light is on and if you’re experiencing engine trouble, a drained battery, or trouble with steering, you may need to get a serpentine belt replacement. 

If you see or hear any of these telltale signs, it may be time for an update. You can also get it looked at while getting your oil changed or by a mechanic if you have concerns. 

If you don’t drive that often, you could be a low-mileage driver and may not ever have to get a serpentine belt replacement. If you do, it may take a very long time until it’s time for an update. 

The bottom line 

Car maintenance is an inevitable part of being a car owner. You may know about your oil changes but not as much about your serpentine belt. Now you have an idea of what it is, how it works, and when to get a serpentine belt replacement. If you don’t drive very much, it may not be something you need to consider as much. 

If that’s the case, it might be time to rethink your insurance to make sure you’re getting the most savings. Using pay-per-mile auto insurance with Metromile, you pay an affordable base rate and several cents per mile. If you pay gas by the gallon, why not insurance by the miles you drive? Grab a free quote today to see about potential savings. 

Melanie Lockert is a freelance writer, podcast host of the Mental Health and Wealth show, and author of Dear Debt. She’s a cat mom to two jazzy cats, Miles and Thelonious, an amateur boxer, music lover, and needs coffee to function.