overheating when turning off car

This 225 stays perfectly cool and runs great while im driving it but when i let idle {after its fully warmed up} for more than 5 minutes than it starts to overheat? Then after i park it and turn the car off its goes up maybe 50 to 60 degrees, i just put a new thermostat in it, flushed the radiator, and replaced the lower hose. what could cause this and how do i fix it? I have a fan shroud but im not currently using it,after it over heated today i noticed a bit of oil dripping out from the oil pan and surrounding areas also it sprang a few leaks of antifreeze after overheating.