new heater core

i put in a new heater core in my 92 grand prix. unfortunately after a week of trying to get the water to circulate to it i give up. its a 3.1 v6 it has two bleeders one above the water thermostat, and the other on the housing for the water pump. ive bled them both only one side of the NEW heater core will heat up i turn on the fan then it goes cold again. i think the way im bleeding the bleeder above the water pump is wrong. does anyone know how to do this im dumbfounded and i don't want to spend another day guessing its almost winter in minnesota and i need the heat before it really gets cold oh btw i changed the metal lines to rubber so they are not plugged and new thermostat and heater core new rad. cap etc im out of idea's and it does not have a heater control valve trust me i went to pontiac and asked they said it didn't come with one.

Jack the right front corner of the car up high enough so the radiator cap opening is the higher than any other cooling system part. If you haven't installed a new thermostat, now would be a great time to do so. If the thermostat (new or old) doesn't have a jiggle valve, drill a 1/8" diameter hole in the t-stat flange to allow air to escape past it when it's closed. Open the bleeder at the t-stat and s-l-o-w-l-y add coolant to radiator until coolant comes out the bleeder then close it. Open the second bleeder at the coolant transfer pipe and do the same thing. Continue adding coolant until the radiator is full to the cap opening. Now start the car and add coolant when the level drops until it's up to the radiator cap hole again. Make sure the heater is set to hot. Slowly let the car down and put the radiator cap on only to the first notch, not tight. Let the car run until the hoses are warm and the heater is blowing warm air. Shut the car off, then as soon as it stops running, re-start the car. Check coolant level in the radiator and add if necessary. Crack both bleeders one at a time starting with the t-stat one and if no air escapes, you should be done.