1996 Chevy Blazer over heating and coolant leak

have you checked the pressure in your system? When your engine is overheating you may either be boiling off coolent or leaking it out or both. you may also be getting coolent in your oil and you can check that by simply examining your dipstick. You'll know if there's coolent in your oil if it's thinned out and discolored. Also check a few different places such as radiator hoses, heater hoses to the heater core, radiator plug, coolent sensor, intake manifold seal, head gaskets, and even an engine plug. The dex-cool thats recommended to use in the gm engines will also build up sludge in your cooling system when you add water causing a blockadge. It can be cleared using a flush but at the same time the buildup can be so bad that it can also woresen your problem by moving a 'clump of sludge' somewhere it can't move through and then you'll defintly have to start taking off parts... Good luck!