I have a V6 2002 auto with cooling problems, but very wierd. About 6 weeks ago she started blowing steam and air out of the expansion tank so a new thermostat and plastic pipes and coolant sensor were fitted and a new expansion tank and black ratchet cap. We did a sniff test and it is clear. The system was bled, and bled, and bled. Sitting in the drive for over an hour without the cap just a small rise and fall in the tank and temp guage dead centre. The heater in full on and heat to the screen no problem. Turned heater to off and ran for half hour seemed ok so put on the cap. It ran for an hour or so spot on. Turned off, no massive bubbling in the tank, left it overnight to cool down and the level was spot on in the tank. Went for a drive up hill and down dale over 45kms, had heater on and off, hot and cold and tried with air con running, spot on !!! Parked up no bubbling etc. Went out the morning after and after 12kms the temp gauge shot up to full then dropped back to normal, it did this 3 times over a km so I stopped and the tank was gurgling full pelt. Trailered it home and left it to cool off, topped up the tank and bled again then ran for an hour with reader on live data, the temp never went above 102 and the tank is gently up and down with heater on full, with heater off she starts to fill the tank. I dont think she is actually overhaeting but whats with the temp gauge jumping up to full then back down ???? bearing in mind I did 40 odd kms up and down perfectly and the thing never moved then she starts bubbling and f----ng again. Any help/suggestions very welcome. Thanks Alan