In today's guide, the serpentine belt on a third-gen Ram with a Cummins 6.7L diesel is being replaced. The belt tensioner is also being changed. Ram recommends replacing the belt around 100,000 miles.
Before removing the belt, it's a good idea to take a picture of the routing diagram for reinstallation. In this case, the belt had already broken. Upon inspection, it appeared something had locked up. After spinning components by hand, it was clear the tensioner was going bad—the bearings were failing, which likely caused the belt to break.
Component Kit and Belt Quality
A component kit was purchased that included a new tensioner and a Gates belt. The Gates FleetRunner belts are considered high-quality and typically last longer than standard belts. These belts tend not to stretch like normal serpentine belts, which are designed to stretch over time. Stretching leads to squealing or chirping, indicating it's time to replace the belt.
Accessing the Tensioner
A belt tool was used to access the tensioner. The easiest method is to remove the airbox. However, in this case, the aftermarket cold air intake was not removed due to vibration issues—it was tied to the battery tray. Instead, access was achieved from underneath the truck and through the fender wall.
By reaching through a hole under the fender well, the tensioner, located on the opposite side of the AC compressor, was accessible. The new tensioner was installed the same way.
Removing the Old Tensioner
The tensioner is bolted to the block with a 13 mm bolt. A ratchet or pipe can be used to rotate the tensioner toward the driver’s side to relieve tension. The bolt was removed from underneath, and the tensioner was pulled out. Some kits include a new bolt, but the old one was reused.
| Component | Check |
|---|---|
| Alternator | Spin by hand |
| Water Pump | Check for noise |
| Idler Pulley | Inspect under top hose |
| Power Steering | Check on driver's side |
| Tensioner | Replace if binding |
Installing the New Tensioner
The new tensioner featured a heavy-duty metal pulley, replacing a plastic one. It was bolted on from the bottom. Once in place, the new belt could be installed. The routing did not require going through the fan shroud. Instead, everything was done from the passenger side.
Referencing the diagram, the belt was routed over the alternator, AC, and around the tensioner. The tight spacing required turning the belt sideways to get it behind the tensioner. If the airbox is removed, access is much easier.
Belt Routing and Adjustment
The belt was routed over each pulley. The hardest part was routing around the tensioner, mounted close to the block. To make it easier, the tensioner bolt was loosened to allow some movement. This allowed the belt to be slid in sideways and then re-tightened.
The Cummins 6.7 serpentine belt from Gates is slightly thicker than standard belts, which makes this method more effective than forcing the belt between the block and the tensioner.
Final Belt Installation
With all pulleys aligned and the belt seated, the tensioner tool was used to release tension while placing the belt onto the alternator. A final check confirmed the belt was seated properly underneath and on all pulleys.
The engine was started, and the belt and tensioner replacement were completed successfully. No more noises were heard from the tensioner, confirming the fix worked. Although airbox removal makes access easier, it is possible to complete the job without removing it.