My uncle lives up in NY, he has had an a/m heater in his 72 Jeep CJ for a few years, he says that its not anti freeze but water builds up on the heater core inside, he said when it gets hot the jeep fills with steam and when he tuns on the fan water runs onto the floor from it, but its clear water, not anti freeze. What would cause this water build up on the heater core? There is no a/c in the vehicle, there is no washer fluid in the vehicle.