my 1990 mustang 5.0 gt recently started blowing smoke from the vents. It smells like antifreeze and fogs up my windows instantly. it doesnt start smoking automatically, it only does it after i drive it for a long time, go over 120 or turn the ac/heater on. havent checked anything yet, i work 14+ hour shifts so i want to know what to look for before going in there and just look around. any help would be good...thanks.