I have a 2000 Accord and for the last 3 days when I start the car, for the first few seconds I smell a light hint of anti-freeze from the vents when the A/C is on. I get a little bit of film if it is on the upper vents. After 10 seconds the smell is gone and does not return until the car cools of for about 2 hrs then comes back when I start it. I see no leak inside car on passenger side but I do not see external leak either. I am bringing the car in on Friday to get pressure tested, but I called a delaer and said they have replaced 1 heater core in 8 years and doubts it is that.

Could it be an external leak I am missing? Compressor, hoses etc...or could the core leaking and not internally? Thanks.