Chevrolet Repair: 1998 Blazer overheating problem, Overheat 4.3

Question
I have a 1998 Chevy Blazer LS with the Vortec V6. It overheats, sometimes, only during the summer when its hot out. We have changed the thermostat and it still overheats sometimes. Could it be the head gasket? We weren't sure cause there isn't any antifreeze in the oil, which is common for a blown head gasket. Or could it just be the water pump or radiator?

Answer
It sounds like the Veins in the water pump are bad.  You will need to replace the entire water pump.  Also you should have the Extended Life coolant in the system which over time turns to a rust color.  A full flush should be done including a flush of the heater core.  I have seen a whole bunch of the blazers have clogged heater cores thus restricting proper flow.  If you don't have an air line to blow through a garden hose will do fine.
Any other questions feel free to ask
Jimmy