I have what looks like a repaired crack in the block of my D2. This is behind the injection pump. I would have never noticed it except I was cleaning the block up after I removed the ip.
My guess is that the crack was caused by water freezing in the water jacket behind number 2 cylinder. Any other opinions as to the reason for the repair are of course welcome.
I'm not really concerned about it. After all it has been this way for at least thirty years without causing any problems.