I have a 03 GT. 208k miles. My car did overheat at 203k. I have sense had a coolant flush done. My coolant looked like a chocolate shake. drives fine everyday sense then. Sometimes it does still get a little hot but never above 210 on my temp gauge. (I have a 180t Stat installed) but my heat does not blow out hot air. I'll turn it on blows out hot for maybe 2 seconds then goes to cold. I believe I just need a heater core flush because it did start blowing cold air out right before my car did overheat. Whenever I select hot or cold on my climate sliders I can hear the actuator or whatever is switching for hot air to cold air but it still blows out cold