Why would the overflow tank from the radiator REMAIN past full?

What is your question?

I just bought a Montero limited edition and LOVE IT!!I always had Hondas before and am trying to get to know this new Mitsubishi. It acts like its going to run hot...then drops quickly. Don't understand? Its blowing water from the radiator...I believe...and the overflow is way past full..? Can anybody help me get to know my new girl...I named her FELICIA! Felicia has ATTITUDE!!! :-)