Losing Antifreeze

[oma14]

I drive a 2012 Mustang Convertible 6cyl. As I was driving to my son's house the heater quit working, it was blowing cool air. The engine was not running hot. It was in normal range.

As I was leaving my son's house I notices a wet area under the front of my car. When I looked under the hood I saw that the antifreeze was almost completely gone.

My husband checked for leaks, ran a pressure test to try to find a leak and found nothing. It held the antifreeze for 2 days with driving short trips and with all the pressure tests and such. He checked the coolant level before I drove to work yesterday and it was full.

I have a 1 hour commute to and from work. Last night he checked it again and although it still has coolant, it had lost quite a bit.

The car never runs hot, so we are not quite sure what to do next.