Cummins 5.9 Engine Belt Diagram: A Complete Guide for Owners

The Cummins 5.9L diesel engine has earned a legendary reputation for durability and performance. Found in Dodge Ram trucks, buses, and various industrial machines, it’s a favorite among owners who value both power and longevity. But like all engines, it relies on smaller components to keep running smoothly—one of the most important being the engine belt.

If you’re planning a belt replacement or simply want to understand how your engine works, knowing the Cummins 5.9 engine belt diagram is essential. This guide will walk you through the basics of the belt system, explain why the diagram matters, and give you tips for installation and maintenance.

The Role of the Engine Belt in the 5.9 Cummins

The 5.9L Cummins uses a serpentine belt (also called an accessory drive belt) to transfer power from the crankshaft to several key components, including:

Alternator – keeps the battery charged

Water Pump – circulates coolant to prevent overheating

Power Steering Pump – ensures smooth steering operation

Air Conditioning Compressor – provides cooling comfort

Fan (in some models) – helps manage engine temperature

Without a properly functioning belt, these systems will fail, leading to overheating, electrical issues, or loss of steering control.

Understanding the Cummins 5.9 Engine Belt Diagram

The belt diagram shows the exact routing path of the serpentine belt across pulleys and accessories. On most Cummins 5.9 engines, the routing is as follows (may vary slightly by year and configuration):

The belt starts at the crankshaft pulley

Loops around the tensioner pulley

Wraps over the alternator

Goes to the water pump pulley

Runs across the power steering pump

Connects to the AC compressor

Returns to the crankshaft pulley

Most vehicles with a 5.9 Cummins will have a belt diagram sticker under the hood. If it’s missing, having a reference guide (or printing one out) is crucial before removing the old belt.

Why the Belt Diagram Is Important

Correct Installation – Following the exact routing prevents misalignment and premature wear.

Time-Saving for DIY Repairs – Even experienced mechanics use diagrams to avoid mistakes.

Essential for Emergency Fixes – If the belt slips or breaks on the road, the diagram helps you reinstall a replacement quickly.

Steps for Replacing the Belt on a Cummins 5.9

Locate the Tensioner

Use a wrench or ratchet to rotate the belt tensioner and release tension.

Remove the Old Belt

Slide the belt off each pulley carefully.

Follow the Diagram for Installation

Route the new belt according to the Cummins 5.9 belt diagram, ensuring proper alignment.

Reapply Tension

Release the tensioner slowly to secure the new belt.

Double-Check the Routing

Make sure the belt sits fully in each pulley groove before starting the engine.

Maintenance Tips for Your Cummins 5.9 Engine Belt

Inspect the belt every 10,000 miles for cracks, fraying, or glazing.

Replace it roughly every 60,000–100,000 miles, or sooner if you notice wear.

Check the tensioner and pulleys during replacement—worn components can cause a new belt to fail prematurely.

Always use a genuine Cummins belt or high-quality OEM equivalent for the best performance and fit.

Conclusion

The Cummins 5.9 engine belt diagram is more than just a routing guide—it’s a critical reference for keeping your engine accessories running properly. Whether you’re performing regular maintenance or handling an unexpected repair, having this diagram ensures correct installation and reliable operation.

By pairing a clear understanding of the diagram with high-quality replacement belts, you’ll extend the life of your 5.9 Cummins and keep it performing at its best for years to come.