Has your water pump ever been changed? Or is it the original? There have been cases where the plastic impellers have broken off and become lodged in various places causing overheating issues. Plus the decrease in pumping ability.
I can't imagine ever X/O of coolant again without the Airlift. It is as easy, fast and brain dead simple as the video shows.
https://www.youtube.com/watch?v=FQnfUe6P5VI&t=29s