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So as some of you know I installed my rebuild 7.3 and had compression in the coolant bottle, my thought was I fudged the head gaskets when I installed the head, once I removed the driver side head there was no failure on gasket.
As I was taking the injectors off on driver side cylinder 4 the injector tip was black where compression was passing by, the copper washer was there and looked thinner than the rest and injector cup was black inside.
I was like failed injector copper washer, the one injector was seated all the way though and I did installed new copper washers. The injector cup had no cracks but the inside of the head you can see black where compression was passing by on the bottom of the injector cup.
So what the hell happened to that cup?
Not sure I want to use this head, there's no cracks on it either. The injector nozzle hole on the head also has some heat marks why would that happen?
Last night reading about your head gasket issue first thing that came to my mind honestly was this. I almost posted Wonder if it is a crush washer on injector causing s cup iss but didn't. lol IMO the cup has to have a hairline crack in it or it is lifting the bottom of the cup up slightly and passing by there pressurizing the coolant system. I would start by pulling thst cup and inspecting it and the head good. See if anything sticks out.
Could the bottom of that injector bore have had a tiny bit of debris, such that the injector cup did not quite seat all the way? That could allow combustion gases into the coolant passage and over pressurize your degas bottle like you mentioned. The copper crush washer would be flattened just a bit more than normal as the injector was torqued down against a slightly raised injector cup. Just spit-balling based on what you and Tpayne are saying, and my own experience of not cleaning the bores adequately.
Found a hairline crack on the head from the middle of the injector nozzle hole in the head all the way to the cooling chamber after removing injector cup and cleaning it with brake cleaner. Took one of the heads off the old mill and took it to the machine shop, should be ready by Monday or Tuesday.
Just to recap, I didn't do injectors cups left old ones in but the problem head was on my old mill that came out of my 95 that had oil in the cooling system and coolant in the oil. At first glance nothing obvious on the injectors that would cause problems unless I had removed the injector cups. Live and learn. Lol
Also why in the world did that cylinder overheated that it blued the head combustion surface? This is what makes me scratch my head.
Possibly it was blowing all the hot compression out the injector hole around the cup into the coolant system when it was the hottest and didn't have anywhere else to go. So the heat was concentrated to that area. But before the exhaust valve was open. Makes sense in my unprofessional opinion.
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