So I have a 94 ls all stock the car runs at normal temp when the heat is off if I turn the heat on the cars temp starts going up slowly and heat is super hot as soon as I turn the heat off the cars temp goes back down, I also noticed I can smell a faint smell of burnt coolant when I get ou the car I dnt smell it in the car. Oil is not milky coolant is full no smoke or anything like that could is be a clogged heater core or a clogged radiator or could it be the intake manifold, one other thing I noticed is even if the heat is off there’s still hot air coming thru not alone but enough to feel if u put ur hand in front of it