Hi, new to the forum and new to owning a merc. I have a vito vito w639 109 and have no heat blowing out my heaters vents at all. I have had heat only on a run at 2400 rpm. Ive changed the water pump and thermostat. Ive Ive the heater matrix cleaned out. That was fine. The water pump was fine also. The engine can sit on tick over for over 45 mins and the pipes are not getting hot. Im not loosing water or oil. Is there a magic fix??