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Spent three days chasing a phantom knock in a 6.7 Powerstroke
Had a 2015 F-250 come in with a light knock only under load. Thought it was a simple injector issue, so I swapped the suspected one. Noise stayed. Checked the turbo, the up-pipe, even pulled the valve covers looking for a loose rocker. Finally found a tiny crack in the exhaust manifold, right where it bolts to the head, that was only opening up when the engine got hot and torqued over. That little hairline crack cost me about 18 hours of diag time. Anyone else been fooled by a noise that turned out to be something simple in a weird spot?
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eric72316d agoMost Upvoted
Honestly though, is a little exhaust leak even that big of a deal? I've heard way worse from a cracked manifold and the truck ran fine. Sometimes you just gotta send it and not overthink every tiny noise.
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averywilliams18d ago
Man, that is the WORST kind of hunt. I had a similar thing with a tick on a Duramax that sounded exactly like a lifter. Turned out to be a pinhole in the EGR cooler pipe spraying onto the manifold. It's crazy how a tiny leak can mimic a major internal sound so perfectly. Those exhaust cracks are the ultimate troll.
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caleb26217d ago
Oh man, I feel that deep in my soul. It's always the smallest thing that makes the biggest noise. I chased a rattle on a Cummins for a week that sounded like a heat shield, but it was just a single loose bolt on the bell housing cover. You get so focused on the big, expensive stuff, and it's always some cheap part laughing at you from a hidden spot.
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