that is true Zman17, because the antifreeze gets soo hot it creates a slight steam affect,( it gets slightly gassy) which is why you are smelling it, fill the resovoir about 2/3's full and watch it for a few weeks, if you still see nothing, but smell it i would not worry about it.

 

aint your head gasket, you would know if that was goin out. white smoke, milky oil, rough runnin motor etc.