1992 volkswagen cabriolet coolant system problems..?

I have had an ongoing struggle with my cooling system since i've gotten the car and it's gotten expensive.. Just recently i had a new radiator put in and all new hoses and reservoir cap but now the radiator seemed to be leaking and the problem before was that it was building pressure and blowing it out my jug.. Now the bottom hose seems to be cold and the top going to the engine is HOT but the little hose going from my radiator to my jug (return flow) or whatever is not working like it used too.. It used to shoot a steady stream of coolant into my jug and now it does nothing.. My temp gauge never moves so it's hard to tell what's going on.. I replaced the thermostat but maybe it was a generic.. Any other ideas what could be going on?