As these models age, we are seeing an increasing number of heater core failures. When the core fails, you’ll get anti-freeze vapor out of the interior vents. Especially noticeable when the defroster is used. Left unrepaired, this can also lead to serious corrosion problems in the floor pan. This is a very time consuming job as the entire dash must come out and the heater housing cases must be split. Plan at least a day with level 3 skills or consider having it done by an experienced shop.