There are only two ways coolant can get into cylinder to be burned off.
Most unlikely is the lower intake gasket leaking coolant into cylinder #1 or #6, coolant flows thru the lower intake from one head to the other on a V engine.
This would usually show up with coolant in the oil as well.
So remove #1 and # 6 spark plugs and see if either looks like it is getting steam cleaned, i.e. coolant burning in that cylinder.
Second, and most likely, is a cracked head or head gasket leak.
4.0l OHV engines have that cracked head cross to bare, head cracks between valve seats because of weak casting, small hair line crack at first, but when it does over heat it will get bigger.
Do a search here for "glove test"
It is a free test for cylinder to cooling system leak.
No, there doesn't have to be overheating at first, but there will be if you don't keep topping up coolant.
What happens is the leak will pressurized the cooling system more than normal so you will see overflow tank fuller than it should be.
And the amount of coolant getting into cylinder while running is almost none since head will have mostly air around the crack.
But when you shut off the engine the cooling system still has pressure in it and this will push coolant into the cylinder which now has 0 pressure, it will vaporize at first because of heat, but eventually it will remain in fluid form, and sit in cylinder until you start engine again, then you get the big smoke show.
Either of these can can hydro-lock cylinder, which can bend a rod or break a piston.
As said my money would be on a cracked head, hope it is just an intake gasket but that is a real longshot.