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Most modern cars have one to three drive belts that help different parts of the engine function. Without these car belts, your car probably won’t run, so it’s important to understand what they do and how to maintain them.

What Is a Drive Belt in a Car?

A car drive belt is a piece of flexible material that helps power a part or set of parts in the engine. It connects the alternatorwater pumpair-conditioner compressor, and other mechanical parts of the engine.

What Are the Different Types of Belts in Cars?

There are three common types of drive belts in cars, namely the serpentine belt, V-belt, and timing belt. What type of belt your car has will depend on its make, model, and year.

Serpentine Belt

The serpentine belt is a long continuous rubber belt that snakes through several pulleys to power various systems of your car’s engine. It transports power from the engine to the air-conditioning compressor, water pump, power steering pump, and alternator. When your engine is on, the serpentine belt constantly rotates with the help of a belt tensioner.

Advantages and Disadvantages of Serpentine Belts

Because of its length, the serpentine belt is easy to spot under the hood. Compared to other car belts, it’s also relatively easy to replace because you only have to worry about one belt instead of multiple ones on most cars with serpentine belts. This makes it the most popular choice of car belt among manufacturers. The 5.3L in Chevy pickups is an exception. There is a separate serpentine belt and tensioner on this platform that only drives the A/C compressor.

If the serpentine belt breaks, the engine will still run, but the alternator won’t be driven nor will the hydraulic power steering pump if the steering isn’t electric. Some vehicles drive the water pump with the serpentine belt, but it’s just as common for the water pump to be driven by the timing belt or chain. In this case, all you’ve lost is the alternator and maybe the power steering, which means the battery will die pretty quickly and the car may be difficult to steer.

Some vehicles drive the water pump with the serpentine belt, but it’s just as common for the water pump to be driven by the timing belt or chain.

– Richard McCuistian, ASE Certified Master Automobile Technician

Take note that serpentine belts almost never break. However, they slip quite a lot when they begin to wear out. Usually, it’s best to replace the belt and the tensioner together because a spring-loaded belt tensioner has an internal damper and a bushing that you can’t see.

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What’s more common is for the belt tensioner to break, and it can happen without warning. Don’t count on that failure happening at a convenient time either.

V-Belt

Unlike modern cars, earlier cars had individual belts called V-belts that ran off a crank pulley and went through one or two engine parts. This means you’ll find several V-belts inside your car, with each belt having a different function. The power steering, air-conditioning, and water pump all have their own individual belts.

v belt tensioner needs replacing
This V-belt tensioner needs replacing because it’s no longer running true. On older cars, the alternator or power steering pump needs to be loosened and adjusted. But if you have a bolt-drawn tensioner like this one, don’t tighten it too much or it can burn out the bearings in the alternator or A/C compressor. | Image Source: Richard McCuistian

Advantages and Disadvantages of V-Belts

Because there are individual belts for different parts, a broken V-belt may only stop one accessory from turning.

However, a broken V-belt will usually get tangled up in the other V-belts and cause them to break or jump off at the same time. But even if this doesn’t happen and you only lose the belt that’s pulling the water pump, the engine can overheat very rapidly to the point of serious damage.

V-belts may wear to the point that they lose chunks of rubber and begin making strange knocking noises that sound a lot more serious than a belt issue. Look for cracks or highly polished areas on the pulley side of the belt. V-belts come in different widths and the length of the replacement belt (as with serpentine belts) must be correct. If the belt is a little too short, you won’t get it on there. If it’s a little too long, it’ll perpetually slip.

V-belts can also be hard to source. If your car is an earlier model, you might need to make a special order and wait longer for V-belt replacements. They also have a shorter lifespan than modern belts, so you’ll have to change them more often. When replacing V-belts, you also have to make sure that each one isn’t too loose or too tight.

See also  Underhood Checks

Timing Belt

Also known as a gilmer drive belt, the timing belt refers to a rubber loop that opens and closes the engine valves in sync with the pistons.

It’s hidden under the engine’s plastic timing cover, where it also connects the crankshaft to the camshaft through a pulley system.

timing belt has teeth as do the crank and camshaft pulleys
Notice that the timing belt has teeth as do the crank and camshaft pulleys, which is necessary to keep the shafts in time with each other. If the belt is even one tooth off, the engine won’t run quite right. If the belt gets old enough that belt teeth shear off, the engine won’t run. On some engines, the pistons will make contact with the valves and bend them so the engine won’t start without major work. | Image Source: Richard McCuistian

As mentioned earlier, some timing belts drive the water pump as you see with the timing belt on the V6 in the photo. Sometimes the water pump is driven by the toothed side of the belt and other times it’ll be driven by the back side of the belt. Some engines with timing chains will be configured with the timing chain driving the water pump.

, Mastering the Different Types of Car Belts

Pro Tips are nuggets of information direct from ASE-certified automobile technicians working with CarParts.com, which may include unique, personal insights based on their years of experience working in the automotive industry. These can help you make more informed decisions about your car.

Pro Tip: Always have the timing belt replaced according to the manufacturer’s maintenance schedule, so it won’t fail at an inconvenient time.

Not all cars have a timing belt. Many cars have a timing chain instead. Most modern engine platforms have moved away from timing belts and are using long chains with nylon sliders and oil-driven chain tensioners.

Watch this video to understand how to timing belts work:

How Do I Know if My Drive Belt Is Bad?

There are several symptoms you can look out for to help you diagnose faulty drive belts.

Aside from an illuminated check engine light (note that a belt won’t usually cause this unless it’s slipping really bad), you might notice a chirping or squealing sound from the engine bay if you have a broken serpentine belt or V-belt, or a tensioner with a worn-out internal damper and bushing. If you’ve replaced the belt and it’s still squealing, the tensioner should be replaced.

You might also find it difficult to steer your car because the belt no longer powers the power steering pump if you have hydraulic rather than electric power steering. Other symptoms include visible cracks on the belt, a faulty air-conditioning system, and an overheating engine.

See also  Low Compression Symptoms, Plus FAQ
cross section of a serpentine belt and its pulley mating
Serpentine belts can be worn to the point of needing replacement while still looking just fine and with no cracks. This cross section of a serpentine belt and its pulley mating illustrates the difference between a new belt (top) and a worn out belt (bottom). Notice that the edges of the belt ribs are gripping the sides of the pulley grooves and that there is a channel between the belt and pulley for water evacuation. The worn belt in the bottom graphic will slip under a load. | Image Source: Richard McCuistian

If you notice a ticking sound coming from the engine or an oil leak, then you might need to replace your timing belt. Other signs of a failing timing belt include a loss of oil pressure, poor acceleration power, and engine misfires.

timing belt on kia engine is showing visible cracks
The timing belt on this Kia engine is showing visible cracks on the back side of the belt. Sometimes in a vehicle like this, the engine can get literally destroyed if the belt fails while driving. | Image Source: Richard McCuistian

How Often Should I Replace My Car Belts?

The answer depends on several factors, such as your vehicle’s make and model, how often you drive it, and the type of belt. In general, most car belts need a replacement every 60,000 to 100,000 miles. However, many advise that it’s best to change your belts ahead of time. Replacing a worn belt before it starts to break can save your engine from potential damage.

How to Get Quality Replacement Car Belts

Ignoring a screeching car belt is generally a bad idea. As we’ve mentioned, these belts perform important roles, driving various components with power from the engine. A slipping car belt will cause anything from annoying noises to difficulty steering. Replace your loose car belt when needed by buying a new one from CarParts.com.

CarParts.com is dedicated to helping you find the best deals. We have different drive belts and serpentine belts available from trusted aftermarket brands. If you aren’t sure which to choose or what you need, reach out to our friendly and helpful customer service team. They’re available around the clock and are always happy to answer any questions you have. They can even point you towards some of the best deals we have on our site for your needs.

If you’re starting to hear the tell-tale sounds of a slipping car belt, it’s likely time to purchase a replacement. Trust CarParts.com today and purchase a new serpentine belt or other car belt before the sounds get worse.

About The Authors
Written By Automotive and Tech Writers

The CarParts.com Research Team is composed of experienced automotive and tech writers working with (ASE)-certified automobile technicians and automotive journalists to bring up-to-date, helpful information to car owners in the US. Guided by CarParts.com's thorough editorial process, our team strives to produce guides and resources DIYers and casual car owners can trust.

Reviewed By Technical Reviewer at CarParts.com

Richard McCuistian has worked for nearly 50 years in the automotive field as a professional technician, an instructor, and a freelance automotive writer for Motor Age, ACtion magazine, Power Stroke Registry, and others. Richard is ASE certified for more than 30 years in 10 categories, including L1 Advanced Engine Performance and Light Vehicle Diesel.

Any information provided on this Website is for informational purposes only and is not intended to replace consultation with a professional mechanic. The accuracy and timeliness of the information may change from the time of publication.

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