[zhunter]

ok, i had to replace the coolant overflow tank because there was a hole in it. After gettin the new one put it, i put the coolant in with the appropriate mixture of water and coolant. i ran the heat so that the coolant would circulate, and the temperature gauge goes to the middle, but the heater blows cold air. I thought that the thermostat was out, but im not quite sure. The coolant doesnt seem to be circulating through the radiator, so i came to the conclusion that the radiator may be having some trouble. i just need to know what i should consider about this problem.

[Roadhawg]

Make sure you purge the air out of your coolant system by opening the high point.
It is located near/on the Thermostat housing.

[Turbostang]

I would check the heater core. Put your hand on the line going in and if it hot, then check the line leaving the core. If it not hot then you have a blockage there.