Hi Everyone, I have a cooling system issue that I am trying to better understand. have a 2004 Accord 4 cylinder. I am experiencing issues with various temperatures coming through my vents. For instance, I have it set on full hot and then warm or cool air will come through. It is inconsistent over a 25 mile trip. Issus I currently have..leaking but not sure from where, Radiator is not sucking back fluid from the overflow when the radiator is low. The temperature gauage is where is should be, no overheating. Do you think the issue is related to a faulty thermostat or that air is getting in to the system? I understand a low fluid condition can cause the heater to not blow hot but I have been making sure that the radiator is full. The temperatures in my area are currently between 25 and 40 degrees F. Thanks for the help.