serenity97

My 2004 se blows out cold air (even when set at 90 degrees) whenever I have the car in park. However, when the car is in motion the heat gets warm in the car. I recently brought the car in to the local Nissan dealership for a diagnosis of the problem. I was informed that their may be air in the system and that a radiator flush ($175) would be required that included using a radiator kit as well ($37.99). I was also told that my radiator cap would need to be replaced ($27.36), along with needing an upper radiator hose ($31.62)....Well after having all of this done everything seemed to work fine, that is until the next moring when I was driving the car and noticed that it was still back to blowing cold while parked with the temp set at 90 degrees. I took the car back to the dealership that same day for a re-diagnosis. I got the car back the next day from the dealership claiming to have fixed the problem. Well everything was fine until the next moring when I was driving to work when I noticed that it was still doing the same thing. I brought the car back to the dealership again and was told that they had only seen this problem on one other maxima before.
I was informed by the mechanic that their may be air getting into the head gasket causing this problem. They stated that they were replacing my old radiator with a new one ($456). Well when I got the car back eveything was fine until the next moring when I noticed again that I was still experiencing the same problem.
What could be causing this problem because obviously the dealership isn't sure. I do not want to keep poring money into this car based on dealership assumptions! I have noticed that you can hear water running through the dashboard whenever the climate control system is off. Pleae advise. I do not want to get rid of the car but may have no other choice, I need heat for the winter time.