The sweet smell is ethylene glycol. If it in you exhaust you have a problem. Head gasket? Cracked head? for a humor sideline, Eastman Kodak used to make a product called Kodak Print Flattener. You take your black and white prints and soaked them in it and dried them and you got a softer pictures - ie. flattened prints. Except we a;so knew it as Dog Flattener. We had a problem call once because a customer had a tray of print flattener and he put it on the floor of his darkroom for some reason. Well his dog drank it. And that was it for the dog. Flattened.

Lesson here, do not leave your antifreeze within reach of pets. Ethylene glycol tastes good and kills them....