Besides the sweet smell of antifreeze in the car and steam coming out of the vents, I noticed this last weekend. Dirty brown water on the floor mat under the dash. Oh joy. Heater core removal time.
There is a drain hole in the heater box to let you know when the heater core goes pop. It was dripping from there and where the box hits the firewall.
Ten minutes later, I already have a mess of hoses and vent boxes on the floor.
I was noticing how nice everything looks back there. Looks brand new when you wipe off the forty years of dust.
This is what separates the standard cable type AC system in Chevys back then and the Comfortron A/C system. A butt load of vacuum lines and that controller. The hose connection up top turns inside and changes which hose gets vacuum, then it opens or closes a door, a diaphram, or some other piece. All the Caddy's had this setup, but this was a rare option on Chevys. To be honest, I'd rather have the standard A/C system. This is over complicated for no reason and it's less reliable to boot. Those vacuum lines are still nice and soft.
Here's a screw up that happened on the assembly line. That vacuum line got pinched behind the heater box bolt. I know the heater box and core has never been replaced because you have to drill out the lower right stud to get the box out. Or, you could remove the fender and inner fender to get to the nut under the hood. The factory service manual says to drill out the stud. That's next.