Just as an FYI, while the engine won't overheat within 30 seconds without the cooling water flow, the rubber impeller blades on the cooling water intake pump might take a beating, although I'm not at all sure how long the intake pump can go without melting down.
The one thing you have going for you are that diesel engines are extremely simple requiring only clean air and fuel with a little lubrication and they'll run!
Good luck with your project and feel free to use profanity while working on the engine. Diesels run much better being yelled at. I think they like the attention!!
"There's a wind in my sails that protects and prevails." - "Six Months in a Leaky Boat", Split Enz