I have a F600 with the 5.9 Cummins, purchased not running, with two batteries she fired right up. Smoked badly, and turbo was pumping oil. While pulling turbo noticed that the freeze plug behind turbo is missing. I have read about the rear plug probs what could cause this? All the other plugs look good. Thanks in advance for any help.

 

The rear plug your talking and reading about is actually on the back of the block and cause by over pressurizing the coolant system in high rpm competition (truck pulling) applications. Yours is def a different issue, clean the lip in the block up install a new one and pressure check the system...