The Serpentine Belt Is A Critical Engine Component

by Don Elliott on June 7, 2012

Nothing can stop a car faster than a broken serpentine belt. The serpentine drives all of the peripheral devices in your car’s engine. These include the alternator, the water pump, the power steering pump, and the air conditioning compressor.

Older cars used the classic v-belt, a separate v-belt for each device. Three or four belts took up lots of space and were a nightmare to keep properly tensioned. And, replacing the inner belt meant that it was necessary to remove and then reinstall all of the outer belts to replace just that one inner v-belt.

By using a single, wider belt, the auto manufacturers were able to save a few inches in the engine compartment. They were also able to use a single tensioner, making serpentine belt replacement much easier. Grooves were added to the belt to eliminate slippage. The wider belt was much stronger, making the average serpentine belt last almost twice as long as the v-belts that it replaced.

Fortunately, the serpentine belt is good at announcing an impending failure. Squealing is the first indication that it is time to start shopping auto service shops to schedule belt replacement service. A qualified technician can make a visual inspection to confirm that the replacement is necessary. The tech has access to several pocket tools that measure belt wear. A serpentine belt can last as long as 150,000 miles, but wear varies widely between vehicles, making the visual inspection necessary.

Replacing a serpentine belt is not particularly difficult if you have the right tools.  First, and very importantly, identify the belt routing diagram somewhere in the engine compartment. If the diagram is not readily available, make a drawing indicating how the belt is routed. If the belt has already broken, it might be time to get online to fine a routing diagram. Most belts can be installed several ways, but only one way is correct.

The tensioner is loosened using a 3/8-inch square socket and a ratchet. Unthread the belt and recheck the belt for signs of wear. A misaligned bracket will wear the belt more on one side than the other. If the serpentine belt failed because one of the peripheral devices seized, it will be necessary to square up the new bracket with the new pulley. Most mechanics will recommend replacing the inexpensive tensioner assembly along with the serpentine belt to assure proper adjustment.

Finally, recheck the tension on the belt after the engine has run for a while to make sure that alignment is correct and the tension is with the high and low marks on the tensioner.

A broken serpentine belt can do a lot to reduce your used car value. Including a belt check in your regular maintenance program might prevent a surprise breakdown on the interstate, or worse, a fried engine. Avoid the trip to your local auto shop for transmission repair and learn about how the serpentine belt operates.

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