Coolant overflow tank not draining?

[IAR]

My coolant overflow tank keeps filling up after 60 miles of driving after a cold start. The water in the rad is then obviously low and this has been happening since the temperatures have gone up in the last week or so. I have had cooling system issues before and I hope it's just something simple I'm missing here.

No other leaks or coolant loss, but manually siphoning coolant to add from the
overflow to the radiator is a pain. Any thoughts would be appreciated.

 

[fritz24]

Change your radiator cap, i just dealt with mine lately. The upper radiator hose kinda like squeezed.