My radiator cap was leaking and getting coolant on my engine so i got a new one to replace it (small cap on the radiator not the overflow tank). WEll i changed it and all was fine until today i notice the truck getting hot, popped the hood and the overflow tank was to the top with coolant, cracked the cap open and it went down to the normal level. So i started the truck up with the caps off and added water to it, not much just a little until it quit bubbling, i figured it had air in the system. I drove it around for about 20 mins and it didnt overheat. Has anyone else had this problem or think i just had air pockets causing this?