coolant leak

ok, i have a 1995 4.3 chevy truck. I am leaking under the dash on the passenger side, i understand that to be the heater core. My question is that i am not getting my coolant to leave the radiator. My truck will register a really high temp, bubble at the radiator, but no release. i have a fail safe thermostat, no pressure in the top line. will the core cause this.

Sounds like it's time for a good coolant overhaul. New heater core, run a flush kit through it, new thermostat and coolant.

sounds like the water pump to me!

Maybe the rad cap isn't releasing either! Have it tested, if not, just buy a new one...make sure it's the right pressure rating for you vehicle, and that it's for a sealed system.