Posted: 06/21/2023
Updated 7/29/25
The serpentine belt is a single belt that handles many tasks at once, sending power from the engine to things like the alternator, power steering pump, water pump, and air conditioning compressor. So without it, you’re not going far…or at least not comfortably.
It follows a very specific path around pulleys. That routing is what keeps all those accessories running at the right time and speed. If the belt slips or breaks, you'll probably notice right away. Think overheating, loss of power steering, or a battery that stops charging. Not exactly ideal.
Right alongside the serpentine belt is something you might not think about much: the belt tensioner. Its job is to keep that snake snug. The tensioner applies the right amount of pressure so the belt doesn’t flop around or slip off. If it’s not doing its job, you'll hear squealing noises or see early wear on the belt. Worst-case scenario: the belt fails altogether.
Taking care of your serpentine belt and tensioner isn’t that complicated, but it is important. Regular inspections for cracks, fraying, or glazing can save you from a way bigger headache down the road. And tensioners, which often wear out along with the belt, should be checked too. Replacing them at the same time can prevent problems later.
The serpentine belt does a lot more than people think. It wraps around different pulleys in the engine and sends power from the crankshaft out to parts like the alternator, A/C compressor, water pump, and power steering pump. Basically, all the stuff that keeps your car from being miserable or undrivable.
If that belt snaps? You lose power steering, the battery stops charging, the engine can overheat, and the A/C quits too. It's one of those parts that seems minor until it fails. Then it’s a big deal. So, it’s worth keeping an eye on before it becomes a problem.
Serpentine belts are usually made out of materials like neoprene or EPDM, rubbery materials that can deal with a lot of heat, oil, and whatever else is flying around under the hood. They’re pretty flexible, too, which helps them wrap around all those pulleys without cracking. Inside, there are usually cords made from polyester or aramid fibers to keep the belt from stretching or snapping under pressure.
Not all belts are made the same, though. Some cars need different materials depending on how hot the engine runs or how tight the space is. It actually matters what kind you use. Best bet? Either check your car manual or just ask a mechanic what works best for your car.
Getting familiar helps when it’s time to replace the belt. And knowing what yours is made of might save you a headache later on.
Tensioners are one of those parts you don’t think about much until something starts squealing under the hood. Basically, they’re built to keep your serpentine belt tight. There's a pulley on a spring-loaded arm (or sometimes it’s hydraulic or automatic, depending on the setup), and that keeps steady pressure on the belt while the engine’s running. Without the right tension, the belt might slip or wear out early, and that messes with all the parts it’s driving.
When you’re replacing the belt, the tensioner needs to be released first. Otherwise, good luck getting it off. After the new belt goes on, tension gets reapplied and you're good to go, assuming the tensioner itself isn’t worn out or jammed.
Keeping the right amount of tension isn’t just about performance. It helps your accessories work like they should without overworking the system. Less slipping, less wear, and way fewer problems down the line. It’s smart to check tensioners every so often. If the thing looks beat up or loose, it’s probably time to swap it out.
Spotting issues with your serpentine belt or tensioner before they turn into bigger problems is honestly one of the smartest things you can do for your car. These parts keep your accessory systems running smoothly, so when something’s off, you’ll usually notice it.
Paying attention to the following signs gives you a chance to deal with the problem before you're stuck with a dead battery, no A/C, or worse, an overheated engine. Staying on top of wear and tear here can save you time and money down the line.
That high-pitched squeal you hear while the engine’s running? Most times, that’s a worn or loose serpentine belt slipping around on the pulleys.
You’ll want to look for cracks, frayed edges, or spots where parts of the ribs just aren't there anymore. That kinda wear means the belt’s probably on its last leg.
If the belt’s starting to look shiny or glazed over, that’s not a good thing. It means it’s been slipping and worn down too much to grab right anymore.
If the belt looks crooked or like it’s not tracking straight across the pulleys, that’s usually the tensioner acting up. Misalignment like that can wear the belt down faster, too.
Belt feels loose and just won’t stay tight? Most likely, the tensioner’s worn out or not doing what it’s supposed to anymore.
You start hearing squeaks, grinding, or weird rattling noises near the front of the engine? Could be the tensioner’s starting to go—those sounds don’t usually just show up for no reason.
If you notice any of these signs, it is essential to have your serpentine belt and tensioner inspected by a qualified technician. Timely replacement of worn-out or faulty components ensures the continued smooth operation of your vehicle's accessories.
Look for stuff like cracks or fraying, or if the belt looks kinda off-center.
Tension’s gotta be right, too. Not too tight, not super loose. Otherwise, things wear down faster and power doesn’t get where it’s supposed to go.
Wiping the belt down every so often helps get rid of junk that can mess with grip.
Try not to run every accessory at once all the time. It puts more strain on the belt than it really needs.
When parts need swapping out, go with stuff that actually meets what your car calls for, not just whatever’s cheapest. If you’re not sure what that is, the manual or a decent mechanic can point you in the right direction.
So, usually you’re looking at somewhere between 60,000 and 100,000 miles on most serpentine belts. Your manual will have the exact number, so don’t skip that. The tensioner wears out side-by-side with the belt, so people usually just replace both together.
Technically, you could totally do it yourself if you’ve got the right tools and know what you’re doing. It’s not the hardest job, but not the easiest either. If it’s not done right, the belt might slip or get chewed up... and then you've got bigger problems. Most take it to a shop and let an automotive technician handle it.
First, look at the belt. If it looks loose or isn’t running straight, that’s a red flag. Also, if you hear squeaking, rattling, or a weird grinding noise from the front of the engine, that’s usually your tensioner telling you it's had enough.
Most people do because it saves time and hassle later. If you leave the old tensioner in there and it fails, the brand-new belt could go with it. Kits usually come with everything: belt, tensioner, maybe a pulley or two, and the bolts.
If you're already messing with stuff under the hood, just give the belt a look. Some cars have tensioners that adjust themselves. Others, you’ve got to do it by hand and check the tension against what your manual says. Don’t just guess. It’s easy to get it wrong.
Arnold Motor Supply has been a leading supplier of auto parts since 1927. Founded and based in Iowa, we have auto parts stores all over the midwest. Order your parts today and you'll be notified via email once your purchase is ready for pickup at your local Arnold Motor Supply or Auto Value parts store.
