Why is 98 blazer overheating and heater blows cold air?
classic symptoms of a blown head gasket.... have someone crank
engine while you look at fluid with radiator cap off..see if
bubbles come out ,that indicates combustion gases escaping into
cooling system. also, see you tube video about combustion leak
detector...you put blue dye in radiator, you pump syringe device
,to circulate dye....if blue dye turns yellow, you have blown head
gasket....you can buy a combustion leak detector on internet for
about 30.00 including shipping ,dye and everything.