D4, 6U engine

Sounds like you got your exhaust temp a bit too high and melted the top off of the piston.

Sounds like the D4 is similar to the D2 in that the pistion/rod have to come out the bottom which means the pan needs to come off.

Kevin

In the 1950's Caterpiller used two piece pistons that had the aluminun top of the piston screwed on and held with little brass pins. My D4 7U sent little bits of aluminum up the exhaust stack with a fine spray of oil when the top of one piston came unscrewed. I would guess you have had a similar failure. I replaced all the pistons and few other parts that failed. It's bad news but can be fixed.

Sounds like you got your exhaust temp a bit too high and melted the top off of the piston.

Sounds like the D4 is similar to the D2 in that the pistion/rod have to come out the bottom which means the pan needs to come off.

Kevin

I did not want to do that, will the pan come off without pulling the engine?

Take the head off as it probably has some valve and seat damage too. With the head off the pistons and rods will come out the top so no problem there. I can,t believe the liner is damaged so you,ll see when the head is off and check the top of it.Don,t just put a band aid on it or you,ll have more expensive troubles down the road.

The head is off, the valve face is somewhat pitted but may be grindable. Seat looks good. I can feel that the cylinder does change size but there is no ring ridge. Is this typical? No. 3 piston is also pitted, I wanted to do rings and rod bearings and 2 pistons. My guess is that the injector(s) was a large part of the problem. The rod boss does hit at the bottom of the linner and there is a large chip as if someone else tried to force it up. Idea? (Both rod bolts are out) Does anyone know the alowable cylinder taper?

Pistons and rods come out the top. If it won't come up and the big end of the rod hits then you have 2 choices. Take the liner and piston out as an assembly or cut the rod in half with the gas axe and take it out in pieces. Sounds to me like you need a rod too.

No ring ridge at the top of the cylinder with the taper that you have, indicates that the last ring job had been done not many machinery hours ago. The ring ridge was reamed at that time. If only our Cats could talk to us, the stories that they could tell us about their selves.

I am still have some d4 rod