So I just bought my 02' HSE about a month ago. Drove it 3000 miles home in three days without so much as an inkling of a problem. Then the overheating began. Replaced the expansion cap which was only 6000 miles old from a heater core job. No overheating for two days then it started again. Replaced the thermostat, no problems for over a week and today she went again. If I let it sit fifteen minutes then the temp returns to normal and I can drive it about a mile when it'll suddenly spike into the red again. Right before I replaced the thermostat it would overheat on me and just as it was about to peak at the top of the red it would drop back to normal and then spike then drop again and repeat that process till it stayed red and boiled over. I'm not leaking fluid anywhere, and there aren't any strange sounds coming from the water pump that I can tell, fan belt is in good shape and she's only got 70k miles so radiator should be good and when I replaced the thermostat I checked the lines and there was no sign of buildup or blockage. I'm about to soak her in gas and torch her. Anyone have any ideas?