My Deep Magenta 2014 Sonic Hatchback is back at the dealers after a 1700 miles road trip because of a TERRIBLE coolant/antifreeze stench coming from vent when the AC is on. It appears to occur after driving 30 to 40 miles so I can only assume it is when the engine gets hot?? Also, it gets worse passing and going up hills. The air conditioning can not be used bc the smell is so strong. Of course the service dept. manager states he is having replication the smell. I refused to take the car back until it is fixed or they can give me another car. In the meantime I'm driving one of their loaners. Any suggestions I can pass on to the service dept. manager would be appreciated.