How to Install a New Serpentine Belt, Fan Belt, or Alternator Belt

inspecting a serpentine belt on car

 John Lake

There are lots of pulleys spinning around under your hood. Engine designers are ingenious in the number of accessories they have managed to bolt onto the front of the engine, drawing their energy from the incredible power of that spinning crankshaft. Everything from the water pump to the air conditioning. But let's not get too poetic about it. All of those pulleys need belts to transfer the energy from the crank pulley, and those belts wear out with all of their spinning, heating, cooling, stretching, and shrinking. It's important to inspect your belts every season to be sure you don't have any worn, frayed, or stretched belts. It may be tempting to wait until your belt wears completely out before you spend the time and money to replace it, but that belt failure will never come at a good time. It would be great if your belt broke as you were pulling into your driveway on a Saturday and had all weekend to fix it, but it won't happen that way. 

If your serpentine belt is worn, it's a fairly straightforward and easy replacement. Count on spending a few hours because there are a number of things that probably need to be disconnected or removed on your vehicle before you can get to the belts and pulleys. Most belts can be replaced without having to do things like drain your coolant or remove any hoses. Read on for some easy tips and photos of the various steps involved in replacing your belts.

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Removing the Old Belt

Fan shroud bolt removal

John Lake

If you're lucky, you need to remove your old serpentine engine belt before you can install a new one. We say that because if you don't need to remove the old one, it's because it shredded itself and is now sitting on the side of the road someplace and cost you a tow truck call. It's a good idea to consult your repair manual so that you'll know what needs to come off before you can properly access your belt or belts, every vehicle is a little different. Most cars have a cover to keep hands or object from falling into the spinning radiator fan, this is called a fan shroud. The part of this shroud at the top needs to be removed. Luckily, it can usually be unbolted quickly and set aside.

*Caution: Never remove the fan shroud with the engine running. Even if your car has an electric fan, this fan can come on at any time, and it's easy for one of your fingers to be in the wrong place at the wrong time. Safety first!

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Adjusting the Tensioner Pulley for Belt Removal

Adjusting the tensioner pulley

John Lake

There are three types of belt tensioners used for serpentine belt systems. All of them involve a pulley. The first type is tightened or loosened via a regular hexagonal bolt on the face of the pulley. This is also the most common these days. Another tensioner pulley uses a square-faced bolt for adjustment, and a third uses a large tab that can be set to a certain position for proper belt tightness. To remove an old serpentine belt, or to tighten up a new one, the tensioner bolt on the tensioner pulley is turned until proper tightness is achieved. Please see your repair manual for the recommended tension on your vehicle's engine.

You may also need to remove your radiator cooling fan to access the pulleys, They are usually bolted onto the back of the radiator or the radiator support, and should be fairly straightforward to remove.

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Installing and Adjusting the New Serpentine Belt

Belt grooves on pulley grooves, and smooths on smooths

John Lake

With clear access to your pulleys, you can now install your new serpentine belt. Remember to align the grooves of the belt with the grooves of your pulleys. Pulleys that don't have any grooves in them receive the flat side of the belt. If you mess up and install the flat side of the rubber belt onto a grooved pulley, it will probably split the belt quickly and you'll be back where you started, but one serpentine belt poorer. After you get the belt wrapped around correctly (there's often a chart under the hood showing the route the belt takes, or you can check your repair manual), you'll need to tighten it using the bolt on your tensioner pulley. You're back in action!