what would cause the coolant to come out the overflow tube all the time

you could have a bad radiator cap, but I'm thinking that you may have air in the system that needs to be bleed out. https://www.youtube.com/watch?v=zUpXgAJ1gjU

Are you filling the coolent reservoir past the max fill line?

still sounds like the cap and just because its new dont mean its good. and like Joemom said check the bleeder screw at the thermastat housing have it open eng running and filling the rad. as soon as coolant comes out steady shut the screw top off the rad. install the cap and shut off the motor.