I just did a complete antifreeze flush and replaced my thermostat. Now my engine is still overheating (I put in the Honda recommended 50-50 mix, with the right temperature rated thermostat). Would this be due to air bubbles still in the coolant system or something else? Also, my engine once it is warmed up, will rev between ~850 and ~2000 rpm. What could be causing this? I need some help here. Anything you can provide would be a help. Thanks in advance.