intermittently wet passenger floorboard and always empty coolant overflow container? (1 Viewer)

[landcruiser3DP]

i had a couple issues i was going to tackle. i got some leads but i was hoping to possibly get some help here.
the long story short is i bought the rig with a rear heater bypass. removed it. then at some point i filled the radiator and kept it filled while idling with the heat on high so i could burp the system. it promptly puked it out under the car and i kind of determined the rear heater lines (on my to purchase list) we're not holding fluid. so i redid the rear heater bypass.
i also reamed the roof drains more than once and checked they were draining under the car.
also i do notice a nice puddle - apparently where it should be (about 2/3rd back in the bay from the front bumper) - under the engine bay after running the AC.
i am assuming that even while i physically could not find that overflo nipple - under some heat shield or something - that the overflow is working properly but if i can find it again after another search i can report back.
on the radiator overflow always being empty i tried a new toyota rad cap. but i'm not sure i have done much more than inspect the seams for reside. and i do see some like the pics below but not much too concerning. that said a new radiator is on my to purchase list.
i also filled it filled the overflow with water and left it on a paper towel overnight. should i try this with boiling gmbh of water?(!)
anyway today (warm day but would have only run AC very briefly if at all) that after spilling coffee and pulling the passenger side carpet mat that to my surprise there is some dampness there again.
if i recall correctly i redid a dryer, expansion valve and clutch fluid awhile back and AC is running nice and cold.
A. on the overflow i am going to inspect lines to see if there is some kind of physical blockage.
B. on the moist carpet i am not sure what to do as i imagine replacing the rear heater and undoing the bypass will not solve the problem.
anyway and legends got any leads on things to check or replace?
THANKS

 

[landcruiser3DP]

more pics.

 

[Rusty Marlin]

The overflow being constantly empty absolutely points to a leak.
The dampness could be a bad heater core, but that makes the carpet and interior smell like coolant, and you didn't mention that in your details.
You filled the overflow with water, this is odd. Is the rest of the system filled with water too?

 

[LandLocked93]

+1 suspect heater core leak.
And a fix thereto is a weapons-grade PITA, best I've read.

 

[robnicko]

Bypass the heater hoses at the engine compartment and trial that for a week or so.
If no coolant loss from the overflow then the heater core(s) would be the culprit - hopefully not !
If coolant loss still happening whilst bypassed then engine or coolant lines / radiator

 

[77mustard40]

I had a different outcome with a self emptying overflow tank, no runs or drips on mine which left only one other place to look. HG failure at No. 6 water jacket. Here’s to hoping you find that leak!