I was at my adopted shop having some work done on my car when I see the horror of the entire dash taken out of a 98 740iL. I ask the mechanic, and he says there was a coolant leak the owner complained of. Well, he's gonna get a 2 day labor bill for a $50 part!
The car had 60k+, bought used, off of the pre-owned program. The build date was 10/97, so it's 2+ years old. The maintenance schedule called for a coolant flush every 3 years, or so I've heard. What happened is that the metal coolant lines going from the heater box through the fire wall to the engine began to corrode. They were aluminum. Aluminum + coolant = corrosion! Especially 60k mile old coolant! There was a nice pin-hole at the elbow of one of these metal lines which sprayed coolant inside the passenger compartment.
Please, if anyone out there has a higher mileage 7. CHANGE your coolant religiously every 30k miles or 2 years! The more maintenance, the better!