1998 Mitsubishi Eclipse engine heating up when car stops or

Of course you checked fluids.

When my Eclipse over heated it cracked the radiiator. I can tell you epoxy does not fix that. But long story short -- when a car overheats and you go the dealer, a good friend of mine is a Honda mechanic, they replace the temp sensor, the themrostat, the radiaotr (if its broke), the fans and the relays.

They take no chances. Its cheaper than a motor. I did all that on my car and never really did figure out exactly what the problem was. But it fixed it.

My car was doing the same thing. We replaced the radiator. It kept doing it. We replaced a fan that wasn't running at all and the thermostat. It still didn't help, so I replaced the water pump and the timing belt. The parts are expensive, but if you have a technical college that teaches an automotive tech class, they can do the labor for pretty cheap. And it does beat buying a new engine and then having to replace all those parts anyway.
My car has 169,000 miles on it and runs like a dream now.