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DIY: Replacing A Serpentine Engine Belt

The serpentine drive belt is what keeps your battery charged, your engine cool, steering easy to turn and keeps you cool when it's hot enough to fry bacon on the sidewalk. But how often do you really think about it? Not often enough I'll wager.
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» Serpentine Drive Belt T/S

To check the pulleys, start the engine and look at the pulleys from the sides while, every once in a while hitting the accelerator. The serpentine drive belt tensioner, and belt, will jump up and down a bit as it adjusts the belt tension. But if you see a pulley wobbling it may have a bead bearing or is cocked on its shaft. If you have a squeal or other noise from the serpentine drive belt at an idle, spray the belt with a small amount of water. If the noise goes away for a while but returns fairly quickly, you probably have a misaligned pulley. Don't use oil, brake fluid or belt dressing. Doing so could very well make the serpentine drive belt unusable.

If the Self-Adjusting Mechanism Indicator shows the serpentine drive belt is stretched or damaged, you should replace it as soon as possible. Before you take the belt off, check to see if there is a belt routing diagram under the hood. Most all manufacturers put the serpentine drive belt routing diagram some where on the inner fenders or radiator support. After you take the belt off and ready to put the new one on is not a good time to find it's missing. If there is no diagram, get a paper and pencil and draw the pulleys and belt routing out so you can reference it when you're ready to put on the new serpentine drive belt. And keep in mind some of the most famous last words; "Oh, I can remember that".

Using the appropriate tool, ratchet and socket, box wrench or male hex or square drive, turn the serpentine drive belt tensioner loose to release the tension while you remove the serpentine drive belt.

You may need a special tool to get at the more hard to reach places, but they are available at most auto parts stores and are not very expensive.

Square Drive Type Tensioner

Tab Type Tensioner

When you have the serpentine drive belt off check the pulleys. Grab each one and rock it back and forth and in and out; then spin it. If it feels rough or loose, the pulley bearing is bad. Since the bearings are generally part of the assembly, such as in the case of an alternator, you will have to replace the whole assembly in order to correct the defect.

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Additional Information provided courtesy of and Warranty Direct
© 2000-2007 Vincent T. Ciulla

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