Thanks for a really nice "how to"; it's helped a lot. I'm in the middle of the process of repairing the blend doors, but I want to reapply a high quality foam to the doors like when it was new, but that's requiring removal of the center of the duct work with the heater core in it. I see no other way to apply foam to both sides, and I'm afraid that just using HVAC tape and no foam might lead to a rattle at some point. So while the heater core is out, I might as well replace that too, since the original is 16 years old. A new one was $45 at NAPA. I'd hate to not replace it and have it start leaking after going to all this work.