On my 1987 190e 2.3-16V, i had an odd experience today. After warming up the engine before coming into work, i started driving. Then about 100meters down the road, i turned on the heater and STEAM came from the passenger and driver's side vents! I have never had this happen before. Also, it only blows super hot air. First thing that comes to mind, is the heater cracked? Any ideas??