Why did the valve fail?

[skylark]

Scratching my butt and pulling my hair out on this one. Here is the story. We bought a 98 K3500 with the 6.5 diesel 79K miles. The owner had been driving it through town and it started blowing white smoke out the exhaust. He took it to the only shop open on a weekend and they had thrown injectors at it and later found out that it had a dead hole. The owner had said that he had a bad load of fuel on the previous tank. He also always used the Standyne fuel additive which I believe because there are two bottles that he left with the truck. I expected it to have a melted piston from a stuck injector but found a bad valve instead. Upon inspection it appears that the valve is fractured. The valve seat was untouched, cylinder walls fine and the piston is perfect. Obviously the pieces went through the hot side of the turbo. The turbo spooled fine, appears ok. Also, kind of tough to see, I noticed that every precup has cracks. So far all I'm getting is smelly hair. What caused this?

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[michael hurd]

Broken / chipped valve and cracked pre-cups sound like maybe the shop tried to start it on ether when they changed the injectors and could not get it bled properly.

 

[great white]

Those cracks are common in the prechamber mouths. You're more likely to have cracks than not on even a low mile engine. Has to so with the inconel material they are made of as much as anything else. There's even a tolerance for how long they can be before you have to remove them from service. Iirc, as long as the crack doesn't cross the gasket seal surface, its good. That's a bit crazy for me and if I were rebuilding for myself I'd replace the cups. In your case where you're going to flip it, I'd put it back together since its withing the published tolerance.

The valve?

Meh, flaw in the parent material that finally let go.

It happens....