I have had this on 2 VTs now. After the gas conversion it intermitted pressurizes the cooling system to the point where it pumps a substantial amount of water from the cooling system and the “TOO HOT” warning displays on the dash. You do get an indication just prior to the too hot warning, the engine runs rough and you get a smell of gas in the cabin, just after that the car boils. As a test you turn the gas off at the tank and the car will run seamlessly for months, within a day of turning the gas back on the same thing happens. The first VT we had the gas control unit changed under warranty and the problem went away. We are still fighting the with the second gas conversion company for them to accept the fact that there may be something wrong with the gas control unit as we have no other reason the suspect anything else. The cooling systems on both commodores where checked and shown to be fine. Don’t know if anyone has had the same problems??
Cheers
Colin