There were some problems with some DD engines in the 90's. Some were replaced under warrenty. From what I remember, Detroit never did send out a recall on the engines. Now, its not possible to get help on the repairs. There are some early threads on this issue.
Having said all of this, there have been very few POG owners who have posted that they have had this issue.
The issue with any engine will be how the previous owners maintained there engines during ownership. You have to keep up on the maintenence and the cooling of the engine.