Buick Repair Questions? Ask a Mechanic for Answers ASAP
The most common cause is the heater core leaking and what you're seeing is residue from coolant that's in the radiator and heater core when you use defrost. The heater core would need to be replaced to fix this issue. Hope this helped you, please let me know.
Probably not, if the outside dew point and humidity readings are right for it to occur.
Ok, check under the cowl then for leafs or debris blocking outside ventilation. The cowl is right under the bottom of the windshield outside and in front of the hood. You may have to remove the shield to see in there real good. Hope this helps you, I can continue assisting you after you have rated me too.
Thanks again, Ron
Ok, the next I would do is a pressure test on the cooling system. Also check the passenger/front floor for dampness closest to the front. the pressure test should reveal this issue though.