Originally Posted By: Kuato
From what I can see, I think sample #1 is the triple digits for Iron, and it has come down nicely since then. My 4.0 throws around 21 ppm Iron in 5000 miles so it's breaking in nicely, as far as Iron is concerned.
Fuel dilution, on the other hand....what head do you have on the engine? Was it reused in the rebuild and is it an 0331 casting?
This is a good point. A lot of the rebuilds I have seen have used rebuilt 0331 heads, and some of them crack. When removing an 0331 head, I only replace it with a NEW beefed up version. I would pop the valve cover and see what casting it has. If its a newer improved casting (02-06) it will have "TUPY" in addition to 0331. It might be worth it to contact Marshall and see what they use. I have heard of people contacting Jasper engines, and they denied the 0331 head as an issue, which we all know it is.
If the head was cracked you would probably be losing a noticeable amount of coolant, which I don't think you mentioned. I don't think this is an issue at this point.
The fuel injector idea could be a possibility, although fairly rare. How easily does the Jeep start after sitting over night? If it has longer crank times, your injectors could be leaking down when it sits.
Making sure the engine temp is correct is also important. I would get one of those IR temp guns and test the temp at different parts of the engine/cooling system. The factory sensors aren't the most reliable in the world.
With all that said, there is definitely improvement. Was this the first run with T6? I would do another similar run and see how it compares. I might do a 5,000 run on Rotella T6 in a friend's 2000 Cherokee 4.0 just to see how it compares.
Maybe they used some sort of sealant containing copper on some of the gaskets when reassembling the engine?