I have a 2002 kia rio cinco changed radiator and fan assembly. Thermostat is out but it still heats up on me! Whats the problem?

Sounds like the water pump if you have had all that done. Remover the filler cap on the engine that says "DO NOT OPEN WHEN HOT" please dont open it when hot. check that it is full and you don't have an airlock (it will fill your header bottle as well if you go right to the top. Start the engine and you should see the water circulating top up if it goes down. If when the engine is running, the water gets blown out with force then I would be looking at cylinder head or gasket problem. If after topping up in the engine water point, and you can see water circulating, top it right up and replace the cap. providing you have no leaks this should have cured the overheating. No circulation means, change the water pump. Hope that helps.