How to replace heater core in 1992 Pontiac Sunbird

it is under the dash in the center of the dash.remove the heater hoses from underneath the vehicle,remove the sound insulaters from under the dash,remove the air duct,and remove heater core access panel screws, remove heater core straps,remove heater core.

heater core???? go ahead and tear out the underneath dash on pass side. there is a cover on it, take the bolts out ...disconnect the lines.... there you go.

buy yourself a HAYNES book on your car, this is not something that can be answered in this small space, rather involved process

Does the car have A/C? I've seen where the A/C evaporator coil springs a leak and it will be soaked with refrigerant oil, then every speck of dust or dirt that comes along sticks to it. Pretty soon it's plugged solid, the air for the heater has to pass through the A/C coil along with the heater core. No A/C, it could be that heater core fins are plugged. Also, some cars have a "cabin filter" if that's plugged it won't allow air to enter the system at all. Call a dealer or auto parts store to see if vehicle is equipped with a cabin filter. Good Luck!

Yes, they typicaly about the same size as a pen. Make sure that it is just water comming out, and not coolant. If water, this is normall from condinsation, if coolant, you will need to change the heater core.

You will need to pull the dash assembly away from the firewall slightly and remove duct work from heater case on right (passenger)side then the heater core cover,the 2 bands that secure heater core,drain cooling system,remove the 2hoses,and swop out old heater core.

REMOVE OR DISCONNECT

1. Negative battery cable and drain cooling system.
2. Raise vehicle and remove drain tube from heater case.
3. Heater hoses from heater core and lower vehicle.
4. Right and left sound insulators and steering column opening filler.
5. Floor air outlet duct and heater core cover.
6. Heater core mounting clamps and remove heater core.

INSTALL OR CONNECT

1. Heater core and heater core mounting clamps.
2. Heater core cover and floor air outlet duct.
3. Right and left sound insulators and steering column opening filler.
4. Raise vehicle and connect heater hoses to heater core.
5. Drain tube to heater case and lower vehicle.
6. Negative battery cable and fill cooling system.
7. Check for leaks.

Remove all plastic duct under dash bord till you find core

The heater core is located there just under the dash in the plastic enclosure. AC parts may also be there. Remove the heater enclosure to expose the core. You will have to disconnect the heater hoses from the engine to remove the core and enclosure. Then inspect the core for the leak, usually at a line connection.
The core can then be soldered or sent to a radiator shop for repair. You should have some expertise in repair to attempt this job on your own, otherwise take it to the shop. Some people would try radiator stop leak since the heater core is part of your cooling system, but I wouldn't recommend it. Remember to replace the anti freeze when you are done.

Aside from disconnecting your heater hoses, the only fix is to replace the "heater core". The "heat" function of your climate control system relies on heated engine coolant to work. The small elbow that you describe, is most likely the condensate drain. The "heater core" and the "evaporator core(for the a/c)", are located beneath the dash assembly in an enclosed housing. The "heater core" should be serviceable without removing the complete housing as with some vehicles. I hope this helps