Cummins 5.9L Diesel Teardown Shows Why These Engines Are Hard To Kill

It had 368,000 miles and significant damage to its internals, but it still ran.

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Christopher Smith

By: Christopher Smith

Sep 14, 2024 at 2:00pm ET

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This 5.9-liter Cummins turbo diesel was pulled from a 2006 Dodge Ram 2500.
It was running poorly at 368,000 miles.
Significant damage was found to the pistons.

Few engines attain legendary status like the Cummins B-Series diesel. It's powered Dodge (and later, Ram) pickup trucks for decades, and the 5.9-liter inline-six featured in this recent I Do Cars video lived a hard life. It came from a 2006 Dodge Ram 2500 used by a roofer, and at 368,000 miles it wasn't running very well. But it was running. After seeing the wear and tear in this engine, that's pretty amazing.

Truth be told, 368,000 miles isn't that much for a diesel but it seems the owner didn't care about upkeep. The video opens with an explanation that the truck was trashed, inside and out. It was used for work, and when the owner finally took it to the shop for engine problems, the whole truck was deemed too far gone to justify the repair cost.

There isn't really much to see through the first half of the teardown. The top end of the engine looks pretty good considering the age and mileage. The first signs of trouble come once the head is pulled, revealing the pistons and upper block. A few cylinders have deep grooves in the wall, and bits of debris are found in the combustion chambers on the underside of the head. Something inside the engine had clearly busted.

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As the pistons come out, we see multiple broken items. Piston rings on three of the six pistons were snapped, rendering those cylinders effectively useless. The bad rings scored the cylinder walls, which in turn scored the pistons. Heavy wear was also found on the camshaft lobes, rod bearings, and tappets. At the very least, this engine would need reboring and a new bottom end to run again. That is, to run properly again. Even with three busted rings and metal bouncing around inside, the Cummins fought to the bitter end.

What caused the damage? The video points to a general lack of maintenance as the likely culprit. That could be infrequent oil changes, using a poor quality oil, or simply ignoring smaller problems until they became bigger ones. In any case, this engine has towed its last trailer. The cumulative problems are too much to warrant a rebuild.