Autoblog and Yahoo may earn commission from links in this article.The Cummins Generation That Comes with BaggageCummins is a trusted name in diesel engines. Its oil-burner motos run everything from Ram HD trucks to buses, generators, and heavy equipment. The 6.7-liter Cummins, in particular, built its name on durability and torque that keep owners coming back, especially those who require a reliable workhorse.But the fifth-generation 6.7-liter Cummins, launched in 2019 Ram HD trucks, has picked up some baggage. Owners and diesel specialists have flagged issues with the valvetrain, which can quickly turn fuel system problems and skipped maintenance into major failures – even fire risks.AdvertisementAdvertisementDave’s Auto Center recently tore down three damaged fifth-gen Cummins engines to get real answers. Instead of guessing or relying on online chatter, they stripped each engine down to see exactly where things failed and which parts took the hit first.Three Engines, Three Failures, One Recurring ThemeEvery failed engine in the video told a different story, with the first engine having melted pistons up front. The mechanics said too much heat had burned away the aluminum, leaving the steel ring insert exposed. In this example, the most likely problem was the fuel system problem, particularly an injector dumping too much fuel and sending combustion temps through the roof.Meanwhile, the second engine looked much better. Its pistons were intact, the cylinder walls were clean, and the bearings looked good. However, the valvetrain showed excessive wear, including damaged push rods, worn rockers, and oiling issues. This made a pattern more apparent, specifically with the fifth-gen valvetrain design. The roller lifters and rocker lubrication seemed to be the weak link compared to older Cummins engines.As for the third engine, it was a mess from the start. There was sludge everywhere, the rod bearings failed, and there was contact between the pistons and valves. Here, neglect was the main problem – skipped maintenance sped up the damage until the engine locked up.Dave's Auto Center/YouTubeWhat Owners Can DoNot all Cummins engines are a lost cause. As with most engines, basic maintenance still counts, especially on a hard-working diesel. For current owners, make sure to stick to regular oil changes with the right product. Using the wrong oil will definitely have graver consequences.AdvertisementAdvertisementAlso, swap filters on time and listen for odd noises – these simple steps can catch problems before they get really expensive. Another thing to keep an eye on is the exhaust temperatures. If they spike, you might have injector issues long before pistons start to melt.Most importantly, don’t ignore early warning signs. Engines have a way of telling you there’s something wrong with them, mostly in the form of a ticking valvetrain, rough running, or metal in the oil. If these things appear, check them out immediately before they turn into a full-blown teardown.StellantisThis story was originally published by Autoblog on May 26, 2026, where it first appeared in the News section. Add Autoblog as a Preferred Source by clicking here.
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