Commodore vapour trail

I REFERRED your problem to Mark Lynch of Carcool Airconditioning for his opinion, which is that the vapour can only be water vapour. It could be either a blocked drain tube not releasing condensation to the outside, so as the heater core sitting at the bottom ``steams'' the water, or a leaking heater core itself. Mark would normally discount airconditioning gas as it is odourless, colourless and tasteless, and besides it would have to have a huge leak to be visible and could only last for a maximum of about 30 minutes until the system was empty. VRs commonly block drain tubes and they need to be probed from underneath the car (they are on top of the transmission, roughly halfway) and should only be probed with a plastic cable tie. Mark says he has seen mechanics stick wire probes straight through the heater core.