A leak as large as you describe may be easier to spot when looking at the firewall from under the hood. Check where the heater hoses and AC lines pass through (they pass through at separate spots, so check them both) - there should be some sort of foam/seal sealing them off. The foam should fit tight against both the firewall and the lines. Also check (wiggle) where the various wire harnesses pass through the firewall - those rubber boots can sometimes come loose and not be super obvious.Also, after stuffing about 4 feet long stripping of 2 x 2 inch dense insulating foam around the blower motor area behind the glove box, I still definitely get cold wafting out from the passenger footwell.
I am getting desperate now. Perhaps the next step is to pull the dash and see where this sucker is leaking from. It just seems silly that a truck of the caliber of a freaking Land Cruiser will fail on something basic like this!
With this issue, its basically unusable for roadtrips in midwest winter![]()