Has it overheated?
Don't be quick to assume there's anything wrong with the head. M103s head don't crack really, unless under severe circumstances.

Has the coolant been changed recently? Maybe any pressure in the system (even though probably not, something basic.)

M103 headgaskets do however have a tendency to leak on the passenger side of the block and drip oil. Also mix oil in the expansion tanks, and in some cases leak both ways.

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Only diesels in this driveway.
2005 E320 CDI 243k Black/Black
2008 Chevy 3500HD Duramax 340k
2004 Chevy 2500HD Duramax 220k