Have you changed out the thermostat.
Might check the temperature with one of those hand held temperature guns to be sure of the degrees.
What coolant mix are you using, I think a 50/50 mix of coolant/water provides the best cooling mix.
Can you take radiator cap off and see coolant moving across the top of the radiator, if not, water pump impeller may have come off the shaft.
If you fill radiator with water, no cap, then remove bottom radiator hose, does the water rush out or or just dribble out slow. If water comes out slow the radiator may be stopped up and needs to be boiled and rodded out.
Good luck and let us know what you find wrong,
Remember: fastest way to ruin a good engine, run with no oil pressure, second fastest way to ruin a good engine, let it get hot due to poor cooling system.