How to Change a Serpentine Belt

Know How Notes – How to Change a Serpentine Belt

The accessories on your vehicle’s engine are driven by a single belt that wraps around 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, require less maintenance (tightening), 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 all of your accessories, namely the water pump. With a V-belt system, 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 how to change one.

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.

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 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.

Serpentine belt pulleys are typically ribbed like this. This is a drive pulley for a power steering pump.

Serpentine belt pulleys are typically ribbed like this. This is a drive pulley for a power steering pump.

 

Idler pulleys (and some drive pulleys) are usually smooth, like this one on Ford 302.

Idler pulleys (and some drive pulleys) are usually smooth, like this one on Ford 302.

 

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.

This is a factory routing sticker on a 2002 Chevy 2500HD truck.

This is a factory routing sticker on a 2002 Chevy 2500HD truck.

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 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.

Take the new belt, make sure the ribs are on the inside, and follow the routing. Leave one pulley off.

With the old belt off, the new belt was loosely wrapped around the pulleys, leaving it off one near the tensioner.

With the old belt off, the new belt was loosely wrapped around the pulleys, leaving it off one near the tensioner.

 

Using a ratchet and socket (some tensioners do not require a socket, just the ratchet head), release the tension and hold in place.

Using a ratchet and socket (some tensioners do not require a socket, just the ratchet head), release the tension and hold in place.

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.

Now, slip the belt over the last pulley and release the tensioner.

Now, slip the belt over the last pulley and release the tensioner.

 

All done, just like new. The common change interval is about every 100,000 miles for most vehicles.

All done, just like new. The common change interval is about every 100,000 miles for most vehicles.

This is a simple procedure for most vehicles and you have the satisfaction of knowing you did it yourself.

 

To learn more about NAPA AutoCare, visit www.NAPAAutoCare.com.

about author

Jefferson Bryant

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.

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