A new radiator cap is probably all it needs there. The non fancy kind probably less than 10 bucks.
As said before, sounds like you need to at least flush the entire cooling system and start from square one. If you keep driving it, nothing good is gonna happen.
Also, removing the oil pump and inspecting it as I outlined is so simple, a chimp can do it. You could have removed, inspected, cleaned it and replaced the relief spring ten times in the time you have wrapped up on this thread.
Have you even done an oil change on it yet? All this stuff is stones and bearskins. If you cannot do it, maybe a used Hyundai is in order.
