i have a 97 lt1 and my car is over heating .... ill drive for about 10 mins around town then go to the country and after about 20 mins of car running the tempeture rises. i know the fans kick on when the ac in on but not sure about if they are not on. i have had this problem before and and it was the temp sensor in water pump.... work fine for about 9-11 months....now a similiar problem... when it overheats now the temp sensor in the radiator blows off... i am not sure if this is the cause of my overheating b/c the sensor comes out or the temp is to hot and blows it out

 

Rent a pressure tester from autozone and test it to see if it hold 18psi. If it has even a tiny leak the water will boil and overheat. Replace that sensor if it is loose. The only other likely thing it could be is a bad water pump.

You can also feel the upper radiator hose to see if its holding pressure. It should be stiff as a board at full pressure.