Unexplained coolant loss, strange smell inside, excess condensation inside. Removed heater core, core was excellent, problem is neoprene O rings on plastic elbows goes hard and coolant leaks out down inside under carpet on passegers side. With mats you don't notice the wet carpet. You can unbolt the heater unit and rotate insitu to get the core out without degassing the air-cond.
PeterN