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How to change your serpentine belt

  Wednesday, 2 September 2015

Because automatic belt tensioners are now standard in most cars, a serpentine belt (also known as a drive belt) is usually a DIY-friendly job.  (This definitely didn’t use to be the case – so double check if you’ve got an old or classic car!)

Follow these instructions, and you should be able to swap the belt around in around 15 minutes.

Check the tensioner arm first

It’s important to ensure that the tensioner itself is where it needs to be before you think about swapping the belt around: a good tensioner belt needs to exhibit a slight vibration of around 1/32 inches or less of movement, and the belt should be able to move smoothly, with no jerks or visible vibration.  If this isn’t the case, then the tensioner is bad, and will need to be replaced first.  (Not a DIY task – take it to a mechanic!).

Check the belt actually needs replacing

Typically, the earlier serpentine belts crack with use.  If you’ve got cracks in more than three adjacent ribs of the belt that are bigger than an inch or so – or, there are four or more cracks per inch on one of the ribs – then the belt will need replacing.  It will also need replacing if you notice any of the following:

• Chunks missing from the ribs
• Torn or frayed fabric
• Glazing on the belt’s back
• Debris trapped anywhere in the ribs

In the case of more recent belts, cracking is less common and you’re better off looking for wear.  Wear is harder to locate than cracking, but there are actually smartphone apps that can detect wear (PICguage by Gates is a good one) – or, you can use a gauge.  Measure the belt out and ensure everything’s level.

Get the right tools

It’s worth picking up proper serpentine belt tools.  The job can theoretically be done with standard tools, but we don’t recommend it.

A standard serpentine belt tool will come complete with an assortment of sockets, so you’ll always find a use for it: it’s worth the investment. 

So, let’s get going

Make a note of the current decal of the belt – you’ll need to refer back to this when adding the new one.  If there isn’t a drawing already there, draw one yourself.

Remove the belt, using the serpentine hand belt tool to rotate the tensioner in order to remove tension from the belt.  It should then be easy to remove.  Slowly release the tensioner once the belt is off.

Using the belt placement tool, you can then route the new belt around the belt path you made a note of earlier.  The belt will usually need to go first around the crankshaft pulley, and then the grooved ones.  Finish the job by sliding the belt into a rounded, non-grooved, smooth roller.

Ensure that the belt is aligned with the pulleys, and that it follows the correct path.  Once this is the case, you can slowly release the tensioner.

This should now be ready to go!

Remember, you can always find new parts at the ASM online store.

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