If you use a large Lisle-type of funnel and keep it filled with distilled water on the radiator while the engine is warmed up and running AND the engine block drain plug is removed, can you effectively flush out all the old coolant without the engine running dry?

 

You probably could - I would speculate that you'd really only flush-out the radiator. Might be smart to cycle open & close the drain plug every few minutes.

Good train-of-thought

 

The cooling system will lack pressure in your scenario. It also won't remove scale and other contaminants in your cooling system. Why not simply use a radiator cleaner with distilled water and flush the system? Then you can drain the remaining cleaner and distilled water for a more effective flush.

 

The impression I'm under is the proposed method is like refilling a draining radiator. You could combine the two responses - run a bottle of coolant flush, and then flush the cleaner with distilled water. My thinking is if you run the cleaner, then drain & fill radiator, you still have cleaner in the block and heater core. So I don't see how it'd hurt if you ran the cleaner, and then flushed with distilled water, putting the radiator cap on to ensure circulation.

I originally typed something along the lines of "run a bottle of coolant flush, and then flush that flush with distilled water." Just keep flushing, we want your z bursting with flushiness lol