[san rensho]

All right, first things first. First fill the coolant system with distilled water. Then start the car and get it up to temperature, and try to purge the system of air as well as you can, just using the manual method.

Now, check for leaks, check in the water pump area and in the coolant cap area. If it holds pressure and there are no leaks, start looking at the radiator fans. It's a pretty complicated system that has two speeds, and it's very common for a resistor to blow out which can cause overheating. If you find fault with the radiator fans, then that's probably all that your problem was, it just overheated once.