How to change the Serpentine belt on a 6.7L Cummins? – 9 Steps Guide [2022]


The Cummins 6.7L comes with a serpentine belt system that is used to power various components including the water pump, power steering, air conditioning, and alternator. The serpentine belt is aptly named; it is a large band that wraps around various wheels and resembles a coiled snake when attached, as seen in the two photos in the article.

Serpentine belt

The 6.7L Cummins Serpentine Belt

The serpentine belt in a 6.7L Cummins is used to power a number of components. I show the various pulleys that serpentine belt wraps around, these are:

Serpentine belt issues
  1. Idler Pulley
  2. Accessory Belt Drive
  3. P/S Pulley
  4. Radiator Fan Pulley
  5. Crankshaft Pulley
  6. A/C Compression Pulley
  7. Accessory Drive Belt Tensioner
  8. Generator

Serpentine Belt Issues

Serpentine belt performance might improve over the decades, as technology delivers new materials for a longer-lasting product. However, they are still belts of soft material that go around in high RPM all the time you drive, or when the engine is on and in idle. As such, it is natural to get belt problems with wear.

The main signs that a belt is failing include:

Squealing or chirping noises

Squealing and chirping occur when a serpentine belt starts to slip. Slippage has threes sources:

  1. Low belt tension
  2. Belt stretch
  3. Pulley and Belt are not working cohesively

When this sign appears, take your vehicle in for inspection to check which of the three reasons stands behind the sound.

Cracks and wear


You might not feel or hear anything, but when you look at your belt, which you should frequently do, if you notice cracks, parts missing, damaged or separated ribs, or uneven wear its time to replace the belt.


Air conditioning or power steering failure

When your power steering starts to fail, or your air conditioner is underpowering, before you check them individually, check the belt first. On some occasions, a bad belt is the cause of many symptoms.

Full Break Down

When your serpentine belt breaks, it will stop activating a lot of engine components, and essentially make your truck impossible to drive safely. When this happens, you have to wait for roadside service, or replace it yourself, if you happen to have a spare belt.

The Check Engine light will usually turn on when there is a problem with the serpentine belt. Also, when you use a tuner/programmer, you will get a DTC warning telling you your belt is an issue.

What are the Benefits of Belt Replacement?

Driving with a worn belt leads to a domino effect that will lead to more expense replacing other parts. You must change the belt at the first sign of wear or other issues. Don’t let the belt reach the stage where it will break during a haul. Replacing your belt regularly is the best option, it is safe and, in the end, maintains a better performance all round. Consider that a standard belt costs between $100 to $170.

Apart from the belt, you should also consider the belt tensioner, since a belt tensioner is a component that will make sure your belt is constantly performing to requirements. As such, check your belt tensioner and invest in a new one if your old unit is underperforming. Remember, an underperforming belt tensioner will lead to a damaged belt. Tensioners cost in the $100 to $120 range.

Serpentine Belt Life

In today’s market, a serpentine belt will last between 50,000 to 100,000 miles. Once you reach the 50,000-mile mark, you have to start considering a change. It’s not worthwhile waiting till its too late. I recommend checking the belt once every 10,000 miles; this will give you an indication of the damage that is occurring, and also lets you check the tensioner too.

Replacing a Serpentine Belt

So now you know what a serpentine belt is, let’s take a look at how to replace one.

To start with, the first time you change the belt be ready for a lot of cussing and frustration, once you are in the correct mindset, you will perform in a Zenlike state and bypass that tension and bad language.

The first time is a bitch! I stand by that statement. Don’t make your first time a world war issue, read up here and make your life easier.

Let’s start replacing:

  1. Pop the hood.
  2. Release the tensioner from the A/C pulley
  3. Remove the airbox
  4. Release the tensioner (undo one bolt) and move it out of the path by rotating it clockwise.
  5. Pull out the old belt
  6. Guide the new belt up each pulley as per the diagram, but make sure you leave the tensioner for last.
  7. Remember there is only one correct way, get it right the first time, use the photo guide to help you.
  8. Now slip the belt over the tensioner, and then rotate the tensioner back anti-clockwise into place and return the bolt.
  9. That’s it; you’re done with the belt, now return the air box, close the hood and test your tension.


Replacing a serpentine belt is actually an easy task, it requires focus and 30 minutes or less. Always make sure you have the correct tools available and have a clean engine to work with. Also, don’t work with a hot engine, and always remove the battery negative when working in the engine area.

I doubt you will have a spare belt, so if you are a full-time truck driver with many miles of daily activity, buy a spare one, it is always handy in cases of emergencies.

About the author

Dave Loman

Blogger, racer, journalist, and rental car expert (in any order you like) Dave Loman. You can follow him on Twitter @bridge2gantry.

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