Encore with disappearing coolant.
 

Hi folks,
I have a 2013 Encore with 33,000 miles. It has started consuming coolant and we can't figure out where. No signs of leaks at all. No coolant in the oil. Can't smell it from exhaust while running. We can smell it after running when we open the hood. My local Buick dealer has had the cooling system under pressure all afternoon to see if anything happens with no luck tracking the problem down. I am hoping someone here can pipe up with any and all ideas.
Thanks much