Okam.... It's possible that the head gasket is slightly flawed due to being hot. It sounds like you may have had a overheating warning rather than a VRO failure warning? How long did you run that engine after the warning horn sounded?


VRO warning = Beep every other second.


Overheat warning = Beep is steady and constant.


Overheating could have caused gasket failure, and if just a slight failure, that would allow a slight amount of water enter the cylinder which would, of course, foul the spark plug.


Bottom line.... Remove both cylinder heads and inspect the pistons, cylinder walls, sealing surfaces of the block and heads, gaskets etc. Install new gaskets if all looks well and torque the bolts to 18 to 20 foot pounds.


Start with the left center bolt, then the center right bolt, then down to the next lower right bolt, then in an ever widening circle.


Let us know what you find.