Dexcool is awful .even when air doesn't get into the system it still turns to crap. Do your self a favor and flush out all the details and run green or yellow. Every GM car that I've owned has gotten that flush, the one that didn't had a continuous issue with the heater core clogging . I wanna meet the guy that decided that all gm cars should have dex cool and remove his genitalia with a dull knife