I started having an overheating issue in the fall. When I ran the heat the engine was fine but with out it on it would over heat in minutes. Had it it tested and no exhaust leak so changed both thermostats and it got a little better.
Did a full flush and pulled the water pump. Looked fine but still put in the new one.
After more flushing I finally changed the radiator and the thermostats again and had leak checked again and still overheating. All the lines are clean and get perfect flow. Checked heater core at that flow seems fine. No idea what else to check or what could be wrong since replaced everything so far, including radiator cap. Help!