I own an Audi q7. My car has been making hissing sound when starting and when idle. I have been driving it for 2 years and I have always had problems with AC.have to refill every month during summer. I've used anti leak too and recently I noticed the car smells like gas on the outside of the car but not inside. I have to leave the garage open for some time when I park in it so the smell could go away. Does anybody know whats going on?