I just purchased a used 2002 Nissan Altima about a week and a half ago. About 3 days ago the flex pipe broke. Yesterday my dealership took it to a mechanic to get it fixed. Upon pick up there was no one to really talk to there, only a gas attendant. Today after driving the car, there is a strong overheating smell and the heater is not blowing as hot as it did. The unusual thing is that the mechanic must have went into my trunk and used up 2 of my full antifreeze jugs and left them there empty. This is obviously some clue to the new overheating smell. Any info on what might have happened would be appreciated.