Runnig hot

if there is no emissions comming out of the radiator fill/ cap...check to see if your hoses are not colllasping

If this is a V-6 the overheating can be caused by faulty lower intake manifold gaskets. GM used plastic and rubber LIM gaskets on these engines and after a while the plastic gets brittle and breaks allowing coolant to go into the engine. It's not easy or cheap to change. I have done it in around 12 hours using new Fel-Pro gaskets and a video on youtube.