Im assuming that the heater core is ok now. I have to ask if anyone may have removed the thermostadt in your car...if there is no thermostadt or if it is stuck open the only heat your going to get is from the motor.
To check this is simple...begin with a cold engine. Where the radiator hose is connected to the top of your radiator...follow it to the other end where it connects to the motor..just beneath where it is connected you will see two bolts holding the thermostadt housing on...remove the two bolts..pull it off and you should see the thermostadt if it is there. (you dont have to disconnect the hose)
If it is there..youll need to check to see if it is stuck open...remove it and hold a lighter to the center core of the thermostadt...if it is not sticking...you should see it move.
Or...you can save alot of trouble and just replace it , they only cost about 3- 10 depending on your car and you can see how easy it is to change...just get a new gasket, maybe some gasket sealer.
Your heater core evidently was old, rusted etc. The water passing through the core is the same going through the thermostadt so it would be safe to assume that part might be alittle old too?
good luck!
