I think he means not removing the oil cooler lines to get that oil out when you do an oil change. Oh, darn it! today is oil change day for my '85 300TD!
I have seen the threads on the cooler come out on the hose fittings. Unless you are starting with a new hose or put some Alunox in the threads I use that stuff religiously on threads, I have even been known to put it on flashlight and caps:
http://www.peachparts.com/shopforum/showthread.php?t=130479&highlight=alunox
Still wish I had my 115 300D with its drain plug on the oil cooler, I wonder why they stopped using that?