I was wondering how you could tell if the head gasket is shot? Lately when you start it up there is white smoke that comes out. I really don't know if it is losing water because I think there might be a leak in the radiator. I just need what are the most common symptoms. The check engine light has been on for awhile. got it scanned and said that the apps is shot. But if the head gasket is shot, would that cause the check engine light would come on and through out the apps code.