I was recently plagued with the overheating while stopped problem. Found a leaky water pump as well as a hole in my radiator to be the culprit for losing coolant and overheating. With the new radiator installed, I just had my first overheat over the weekend, and just noticed that the overflow hose directly next to the main coolant fill had popped off (this had happened in the past, so when the new radiator was installed, i made sure to look at this. noticed they did not use a hose clamp from the dealership) The overflow reservoir was not overfilling and meets up with the indicator line on the tank.

My question is what could be causing the hose to pop off? I realize its a pressure buildup, but kinda stumped as to what could be causing it. Again, new water pump, thermostat, radiator, radiator hoses, and negative test for oil in coolant. I know the easy answer is head gasket, but Ive had 2 honda dealerships confirm all tests are pointing to the head gasket being fine

 

Bad or non-conforming radiator cap, clogged coolant passage(s), bad temp switch.