Q: Where would the radiator drain plug be located on my vehicle? 2003 Chevrolet Impala

Hello, the radiator drain plug will be a the bottom edge of the radiator, facing the engine (passenger side). If you drain the coolant, be sure to catch it with a pan of some sort, and properly dispose of it. It will poison animals, and contaminate ground water. Most likely, your radiator is clogged, given your high mileage, and needs professional cleaning, or replacement. The newer radiators use plastic end-tanks, which are often best exchanged for new ones. I would recommend a cooling system inspection by a mobile, professional mechanic, such as one from YourMechanic, who will come to your location, confirm this diagnosis, and give you an accurate assessment of damage and cost estimate for repairs.