1991 Cadillac Seville V8 Two Wheel Drive Automatic 60000 miles
Can't get any heat, at any engine temp. Have replaced the control unit in the dash, checked the flapper valves, and have tried to flush out the heater core which is hard to get to. My mechanic doesn't want to replace the core because he says it's too hard and not worth it.
How hard is it, and are their things we haven't thought of?