heater core haters unite!

I had one go in my old 85 Capri. Actually twice. Once under warranty.
The second time I had to fix it myself. It was a royal pain. Had to remove
the dash. Antifreeze does not lend itself to easy cleaning off your inside
of the windshield either. The reason you may not see any leaks on your
floor is the heater core is in a box with the AC evaporator. If your car
does not have AC it may be easier to fix. If it does and Ford still builds
em the way they used to, it's a pain in the butt. You have to get your AC
unit discharged as you will most likely have to disconnect it to get the
unit out. It took me 8 hours to remove and replace that one. It was the
first time I had ever had to do one, so might have gone faster but had
to take my time. It was also late October and kind of cool having the
doors both open to work. Good luck with it. Maybe it's a hose, but I
kind of doubt it.

Regardless of the setting on your dash if it's hot or cold, coolant/antifreeze will still cruise through the core. I would think it's a matter of physics with the steam--the warmer the temperature, steam will not be as visible as if it was cold. Think of it like breathing outside in warm weather vs. cold weather. The only other recourse is to bypass the core by hooking the hoses together under the hood.

had to change the core on my 94 four times. It became a every other year thing there for a while.