So I have had this issue for a couple of months now. My '02 Rover overheated. Not a big deal, refilled it and it kept happening. Burped it many times, replaced the thermostat, still kept overheating. It started pushing a little fluid out of the overflow at some point I don't know when, that could be what caused the initial overheat, and I didn't notice till I started monitoring it everyday.. After about 80 miles it loses enough fluid to overheat. I refill it and its fine again for another 80 miles. Replaced the expansion tank cap twice and the expansion tank itself after noticing that it steams after being driven. No boiling just a slow gradual release of pressure. The steaming has gradually decreased till its not noticeable now unless the engines off and you put your ear right next to the cap so that may normal I'm not sure. Blew out the radiator to see if it wasn't getting enough air flow but still keeps pushing fluid. It has to be coming from the radiator bleed hose to the cap and then out the overflow because the level never gets high enough in the tank to boil over. Thermostat stays just on the cool side of the middle of the gauge right until it overheats again then shoots into the red. But like I said thats only after its pushed enough fluid out that it's no longer able to cool down. Anyone have any ideas?????