Thanks for the advice. I’ll look at the seal today. (Everything on this car is 20 years old. That’s my main concern about it. “Outstanding condition! Runs great!” Really. I just need to swap out all the elastomer parts.)
Car will be used but little until it goes to the mechanic.
I’m aware of the dangers of CO. I even posted about it here:
Why is my 2001 BMW 530I giving me a headache from heater fumes One of my few positive contributions on this forum.
(I sort of remember advising one poster having headaches and nausea that “Your car is killing you,” but I can’t find that.)