so i was driving home from work today and my car started over heating on the highway so i pulled over and let it cool down the temp went back down and i drove home the temp kept going up and down but spiked especially when i would load the motor on hills. not sure what the problem is ive already flushed the coolant with in the last month ive pressure tested the cooling system and it held ive even unplugged the ac comp so i could force the fan to stay on i dont get it im guessing t-stat but maybe im missing something?