According to the previous owner of my 7J D4 he had problems with the top of the pistons coming off. Now I have the pistons of a 2T D4 engine out with the intent of overhauling it as a replacement engine. One of the pistons has a gap at the top like it was coming apart also. Has anyone heard of this problem or any solution to it?
Also my RD4 book talks about etching, is that still a recommended practice? I do not know about anyone doing it anymore.
I thank you for any input and also for your previous advice on minimum fuel pressure needed to run diesel.

Yes at the dealer I have seen dozens of them that came apart or got loose so the best thing is get rid of them & get the later one piece pistons as the two piece can come apart & raise all kinds of problems inside the cylinder & to the head & even the crank.I kind of doubt if etching is done anymore but years ago I did see the knurling done once in awhile to the pistons.

Best bet on the two piece pistons is to get rid of them. They were a mistake which Cat eventually corrected. The etching process is obsolete and was replaced by the ball type abrasive hones.

I had one of the two piece pistons come apart on my D47U and it wasn't pretty. The top of the piston came out the exhaust in a million pieces while it bent a connecting rod, trashed valve components, rod guides etc. When we dropped the oil pan it looked like Humpty Dumpty. Several thousand dollars later, and a lot of hard work we had it all fixed. I would not want to repeat this experience.

Doug, I know what your saying as I,ve seen it happen over the years back with them when they come in the dealer to repair.

Thank you fellows I will be changing the pistons. Concerning senior members mention of knurling. As I recall and please correct if I am wrong, that involved punch marking a worn piston to expand it slightly to make a better fit and also to relieve any stresses.

That may be the "poor mans" emergency version but the correct method is applied while chucked in a lathe and a knurling tool (roller) applies the cross hatch knurling pattern. Rarely done to pistons anymore........another lost art.

Groove inserts is apparently another lostg art. Does anyone put top ring groove inserts in anymore? Is there any place to get the inserts? I believe Perfect Circle made them, maybe other manufacturers. They were an inexpensive way to fix up a piston as good as new, some say better, if it is otherwise not severely worn.

Cat also made thicker rings to use in the top ring groove after it was cut to fit.I cut lots of them & installed the thicker rings at the dealer while I was working yet.