When you are looking at a previously owned Ford or International diesel, ask the owner if he kept up on the coolant additive. A post above refers to it as F15; it might be FW15. There are also International products that are the saem ( it is their engine after all).
Watch the owner's reaction. If you see a "cloudy" look in his eyes, followed by a quick " Yeah, we did everything", or if he says. " What coolant additive?". Keep your hand on your wallet and leave.
These International enginer are great, but they are susceptible to cavitation UNLESS the owner maintains his coolant additive package.
AFAIK, there is no way to inspect for cavitation. You can check the protection in the coolant right now, but you can't know whether or not it was maintained for the life of the engine.
If you see that the previous owner has added a coolant filter with a dispenser for the additive, you got a good one, ( most likely).