I have a 1999 Pontiac Grand Am GT and it is overheating. We have changed the thermostat, water pump and tried flushing the heater core. It didn't work the car is still overheating and when the heat is turned on cold air is coming through please help!

If you have done all you said you have their is only two things left i know of that will cause them to overheat and the first thing is if its the 4 cyl 2.4 litre it is probably the head gasket blown really common on the 2.4 engine. If it the 3.1 litre engine they have two bleeder valves that when you flush the out or they get low on antifreeze they get air in the line and stop the flow of antifreeze getting threw the engine causing them to overheat and possibly damage your engine. Hope this helped out with your overheating problem.