I HAVE A 2004 CLASSIC
No white smoke? Any puddles Under the car?
Have a pressure test done. Check your oil for contamination. It's going somewhere.
It might not be running hot yet, do what boholmark stated before it goes completely south.
Check the water pump for liquid after shutting it off. There is a weep hole that will bleed off the coolant if the bearings in the pump is wearing out. (most common area to look at.) As stated above. if you can park on a known dry surface, let it stand for a time then back away and check for water/coolant. If you run an A/C, you will have condensation puddles there also so do the swipe and smell test to see if the puddles smell like anti-freeze. The hoses under pressure will exp-and and if there is a small hole or crack, it will pump out liquid also. Squeeze the hoses and if they're spongy, replace them. See if the radiator cap is good. Under pressure it may be weak and let liquid to run out the overflow. Do you have a radiator overflow collector? Make sure it is not leaking and the hoses and connections are good.
Looking for a Used Classic in your area?
CarGurus has 387 nationwide Classic listings and the tools to find you a great deal.
Search Chevrolet Classic Questions
Chevrolet Classic Experts