If you're old enough to remember the good old days when you changed your own fan belts, then you can also remember the bruised knuckles and cursing that went along with it. And to make matters worse, there were often two or three belts to change.
Now, instead of separate belts for each component, most cars today use a single wider, multigrooved “serpentine” belt, named for the way it snakes around multiple pulleys.
Serpentine belts are easy to change because today's automatic belt tensioners eliminate the need to loosen bolts or pry components into position for retensioning. Just rotate the tensioner, remove the old belt and install a new one. When the belt ribs are seated into the pulley grooves, release the tensioner and you're done.
Check the tensioner first
If your tensioner is bad and it’s one of the more difficult
styles to replace, you won’t want to waste your time
changing the belt. The shop would just have to remove
the belt again to replace the tensioner. So check the
tensioner first with these three tests.
The first test is a visual inspection with the engine
running to assess the dampening feature of the tensioner.
Pop the hood, start the engine and turn on
the AC. Then shine a light on the belt tensioner and
observe the tensioner arm roller for excessive movement
(Photo 1). If it passes the visual test, move on
to the “crank” test (Photo 2). The tensioner arm
should rotate smoothly during crank and release
with no binding. If the travel isn’t smooth, replace
the entire tensioner. Next, check the condition of the
tensioner arm pulley/roller (Photo 3). If the pulley or
roller exhibits any roughness, binding or noise, that is
also cause to replace the entire tensioner.
Many tensioners are readily accessible and attach to
the engine with a single bolt. To replace that style,
simply remove the belt and then the retaining bolt.
Pull off the old tensioner, noting the location of the
locking pin on the back. Then slide the new unit into
place, lining up the locking pin with the hole in the
engine. Hand-tighten the bolt and then tighten it
with a torque wrench to the factory specifications
shown in your shop manual.
How to tell if you need a new serpentine belt
First-generation serpentine belts were made from a nitrile compound that cracked
with use. If your belt has cracks in three or more adjacent ribs within a 1-in. span, or
has four or more cracks per inch on a single rib, it’s time to replace it. You also need a
new belt if you notice any of these conditions: chunks missing from the rib area, torn
or frayed fabric, glazing on the belt’s back side or debris trapped in the ribs.
Starting with the 2000 models, carmakers switched from nitrile to ethylene propylene
diene monomer (EPDM) belts. EPDM belts last much longer and don’t crack
or lose chunks the way nitrile belts do. But they do wear, and that wear is much
harder to detect. You can measure EPDM belt wear with a gauge or a smartphone
app. Both products are available for free from Gates Corp. (go to gatesprograms.com/beltwear and click on either tool).
In most cases, you’ll want to use the plastic gauge to measure your belt, as shown
above. However, if you have a smartphone and enough maneuvering room to shoot a
close-up photo (engine off), let technology do the work for you. The app works by analyzing the width of the ribs compared with the width of the grooves.
Always buy premium belts instead of economy grade — you’ll get almost twice the mileage.
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The right tools make it a do-it-yourself project
You can replace a serpentine belt with ordinary hand tools. But we don't recommend it. The spaces are often tight and the belt-driven devices difficult to reach. Using a serpentine belt tool to loosen the tensioner and a belt placement tool to position the belt, we completed the entire job in less than 15 minutes, without breaking a sweat (or a knuckle). The serpentine belt tool comes with an assortment of sockets, making it the perfect choice for all the cars in your family. The two extension bars can be configured to reach the tensioner at the proper angle, and the extra-long handle provides maximum leverage so you can release the pressure easily. The belt placement tool allowed us to remove and properly place the new belt without reaching down into the pulley area.
Note: If your car requires the removal of an engine mount in order to remove the serpentine belt, or the belt's just nearly impossible to get at, we recommend you leave the job to a professional.