Customer called complaining of water in the engine oil on a D6D. Long story short, his water pump started leaking at the weep hole and they drove a freeze plug into it to stop the leak (we drilled the hole to pull the plug back out.) It definitely stopped the leak and also melted the grommets in the head when they didn't see the water pump was transferring the cooling system into the oil pan. Maybe they should have checked the oil more often, I dunno. On a related note, always remember to check weep holes for dirt dobber nests.
That guy needs one big "dope slap"! I hope you adjusted the bill to include an extra few percent for, "Education". Agree on those nasty dirt(mud) dobbers! they are almost as bad as someone putting a freeze plug in a weep hole! If someone did that to my 3306 I'd be wanting to drive a plug into his "weep" hole and see how he likes it!