The accessories on a modern vehicle’s engine are typically driven by a single belt that wraps around all the pulleys. This is called a serpentine belt. Older vehicles used multiple drive belts called V-belts. Starting in the late 1980s, the serpentine system began replacing the V-belts. Serpentine belts last longer (thus less serpentine belt replacement), require less maintenance (tightening), are easier to service, and reduce the drag on the engine. There are some drawbacks from serpentine belts, however. The main problem with a serpentine system is that when the belt does break, you lose power to all of your engine driven accessories, namely the water pump. With a V-belt system, almost all of the belts help drive the water pump, so you can usually at least limp down the road. If the serpentine belt goes, you are done until you get a new one. This is where preventative maintenance is your friend. You need to know the signs of a bad serpentine belt and the steps for serpentine belt replacement.
Serpentine Belt Failure Warning Signs
There are warning signs for serpentine belt failure beside a catastrophic failure that pitches the belt down the road. Take a few minutes every month to look under the hood for the following signs:
Noise – A worn serpentine belt can start slipping. Because of the design of serpentine systems, slippage should not occur with a good belt. Slipping can cause the belt to break or come off, leaving you stranded. Unlike a V-belt that is slipping, a squealing serpentine belt should usually be replaced. Belt dressing is for V-belts, not serpentines.
Cracks – All serpentine belts have ribs running lengthwise. How many ribs the belt has depends on the width of the belt. If the ribs are cracked or sections are missing, it needs to be replaced right away. Be aware that modern belt materials are less prone to cracking than in the past, so a belt can still be worn out and not crack.
Fraying – All drive belts are similar to tires in construction; they have cords inside them to hold the belt together. As the belt wears down, the cords can start showing, specifically on the edges. Once your belt starts to show the fabric cords, it is time to replace it. Misalignment from bad bearings in your accessories or pulleys can also cause frayed belts.
Peeling – Another issue is when sections of the belt start delaminating from the rest of the belt. This is called peeling. Just like hangnail, little pieces of the flat non-ribbed side can start to flake off. Replace it at once.
Glazed – The edges of the belt should be the same color as the rest of the belt. If the edges are shiny, then you likely have an issue with a bearing on one of the accessories or support pulleys. This shows a misalignment in the system that needs to be addressed. Glazing can also be caused by a worn belt or worn out tensioner, allowing the belt to slip.
Oily – If your belt is oily, then you have a leak from one of your accessory components. The belt should replaced, along with the leaky component.
Worn Down – Modern serpentine belts wear down just like a tire loses tread. While the belt may look find, if the rubber belt material has worn down then it can’t grip the pulleys as well as it used to.
If you notice any of the above problems, just change the belt. Serpentine belts are relatively cheap, and typically less expensive than a tow truck ride home.
Know The Parts
Serpentine Belt Replacement
Replacing the belt is not tough, but you need to know the routing before you take it off. Most vehicles have a sticker under the hood with the belt routing. If your sticker is missing or worn, take a picture or search the internet. You must use the factory routing in order for the belt and accessories to work.
All vehicles are different; you may need to remove some components to get to the belt. These may include radiator, fan shroud, and braces. Some vehicles require removal of an engine mount. You should research your vehicle to know the exact procedure.
Once you have the vehicle ready for the new belt, you will need a serpentine belt tool, wrench, or ratchet with the correct socket to release the tensioner. Most vehicles uses spring loaded tensioner that adjusts itself to maintain proper tension on the belt at all times. The wrench is used to pull the tensioner away from the belt so it can come off. Now you can release the tensioner.
There are also vehicle that use one of the engine accessories to tension the serpentine belt. For example, some Toyotas use the alternator as the serpentine belt tensioner. Typically one of the mounting bolts acts as a static tensioner. Simply loosen the mounting bolts until the belt can be removed.
Take the new belt, make sure the ribs are on the inside, and follow the routing. Leave one pulley off.
Once again, use the wrench to remove the tension from the tensioner, and slip the belt over the last pulley. It does not matter what pulley you choose. Release the tensioner. At this point, the belt should be tight and resting in the grooves of every pulley.
Serpentine belt replacement is a simple procedure for most vehicles and you have the satisfaction of knowing you did it yourself.
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A life-long gearhead, Jefferson Bryant spends more time in the shop than anywhere else. His career began in the car audio industry as a shop manager, eventually working his way into a position at Rockford Fosgate as a product designer. In 2003, he began writing tech articles for magazines, and has been working as an automotive journalist ever since. His work has been featured in Car Craft, Hot Rod, Rod & Custom, Truckin’, Mopar Muscle, and many more. Jefferson has also written 4 books and produced countless videos. Jefferson operates Red Dirt Rodz, his personal garage studio, where all of his magazine articles and tech videos are produced.