Hey guys, I've got a buddy with an 02 lb7 that's our work truck. When I started working with him he was loosening the cap on his coolant take everytime he shut her down so it wouldn't hold pressure and leak into his cylinder. I pulled the glow plugs and pressurized the system and sure enough the number 6 cylinder was full of coolant. Radiator hose doesn't stay hard, so I was leaning toward a cup. Especially since it was only the one cylinder and he said it started right after he had his injectors replaced. So I tore it down and pulled the cup, no cracks or anything, but to be safe I cleaned the bore out spotless and used red loctite gel and a brand new cup and o rings. Bolted injector back in right away, then let it sit 24 hrs before adding coolant. Ran great. Better than it ever had he said. Then the 4th day after he ran it for a few hours while it was real hot out and the next morning hard start and white smoke. Burning coolant like crazy. So I tore it back down and did it all again, but used red hi temp loctite and another new cup. Waited 36 hours, rand great for 4 days, ran it long one day and then it did it again. Hard start and eating coolant. It's gotta be the cup since I replaced it and it stopped both times, but how after a long day of running is it making the cups leak? Bad head? Any ideas please. Thanks guys.