10-4 Magazine / July 2026 17 The Performance Zone: By Bruce Mallinson My name is Jordan Greathouse. I have been involved in this industry for 12 years, with the past 10 here at Pittsburgh Power. Over that time, I’ve heard plenty of stories about catastrophic engine failures (every mechanic has). You hear about connecting rods leaving the block, engines scattering parts across the shop floor, and repair bills that make truck owners question their life choices. Somehow, though, despite spending more than a decade around heavy-duty diesel engines, I had never personally witnessed one happen. As it turns out, I still haven’t. But what I did hear was something that sounded a lot like a shotgun going off somewhere else in the shop. A few moments later, several technicians were headed toward my office with expressions that told me whatever had just happened wasn’t going to be cheap. The way they were trying to explain it sounded like one of those over-the-top movie scenes where something so ridiculous happens that nobody expects you to believe it. Naturally, I followed them out to see what all the excitement was about. The engine in question was a Cummins ISX 870. The owner had brought it to us because he was experiencing power issues after a recent rebuild that was performed by another shop. Nothing about the original complaint was particularly unusual. Trucks come through our doors every day with performance concerns, and our process for diagnosing them is pretty straightforward. The first step is getting the truck on the dyno. For those unfamiliar with how our dyno process works, we don’t immediately jump into power runs. We begin with a controlled warm-up procedure, allowing the engine to run under its own power, while monitoring oil pressure, oil temperature, coolant temperature, fuel pressure, and a long list of other operating parameters. It’s a simple process designed to make sure everything is functioning properly before moving on to more extensive testing. Unfortunately, this engine never made it that far. According to the guys running the dyno, everything appeared normal during the warm-up cycle. Temperatures were coming up, pressures looked good, and there was no obvious indication that disaster was only seconds away. Then came the bang. When the dust settled and the technicians began inspecting the aftermath, the cause became fairly apparent. The engine had suffered a catastrophic connecting rod failure, and the evidence pointed toward improper torque specifications during the previous rebuild. The rod cap bolts had been stretched far beyond what they were designed to handle. At some point, the stress on those fasteners became too much. Once the engine was running, the weakened bolts finally reached their limit and sheared completely off. From there, things happened exactly as you’d expect when a rod suddenly decides it no longer wants to remain attached to the crankshaft. The rod and cap assembly were launched into the side of the engine block with tremendous force, and the resulting damage was astonishing. The impact blew a hole nearly two feet wide through the side of the block, turning what had been an engine just moments earlier into a very expensive collection of scrap metal. Oil, coolant, and various internal engine components immediately found new and exciting places to be! There wasn’t much left to diagnose after that. The block was THE MOST STUBBORN CUMMINS ISX 870 EVER destroyed, the internal components were destroyed, and the cleanup process quickly became the primary focus. Needless to say, this 870 Cummins ISX engine was done. As dramatic as the failure was, the situation turned out to have a somewhat fortunate ending. After speaking with the owner, we learned that the truck was already nearing the end of its service life. He had already moved into another truck, and this one was ultimately destined for the scrapyard anyway. While nobody enjoys seeing an engine self-destruct, at least this wasn’t a situation where someone’s daily livelihood suddenly disappeared overnight. Then the story took one final turn that nobody expected. As the guys were preparing to bring over a forklift and move the truck, one of them noticed something strange – the engine was still running. Even with a massive hole in the side of the block and enough missing parts to fill a bucket, this old Cummins wasn’t quite ready to quit. Somehow, some way, it continued chugging along under its own power, and what happened next honestly impressed everyone in the shop. Rather than being dragged into a parking spot, this wounded engine managed to limp itself there. Against all logic and mechanical common sense, it drove itself to its final resting place. I’ve seen plenty of engines over the years. I’ve seen worn-out engines, neglected engines, abused engines, and engines that should have died long before they actually did. But I’ve never heard of one taking that kind of punishment and still refusing to quit. You almost have to admire the determination. Or maybe it was pure spite. Either way, it’s a reminder of how important proper engine assembly procedures really are. Something as simple as incorrect torque specs can eventually lead to a catastrophic failure. Attention to detail matters. Precision matters. Following proper procedures matters. It’s also a reminder that diesel engines can be remarkably stubborn. This Cummins ISX may have reached the end of its life that day, but it certainly went out with a story worth telling. n
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