about 3-4 weeks ago i replaced my heater core which was in fact leaking. been out of town for a couple of weeks and the car was only driven 3-4 times while i was gone. today i decide to check the coolant level since it's had time to really circulate through the system, and it was just a little low, with the recovery tank being empty. first thing i think of is that the core is leaking again... well, i check the floorboards and what do i find? a puddle of water... BUT... i pull up the carpet, the firewall below the heater core is bone dry. i took off the dash cover and it's bone dry. i took off the heater core cover and it is completely dry. i'm now like WTF? the car was driven last night, too, so if the core was leaking, i would think somewhere in that area would be wet. Now, when i found out my core was leaking, i had to pull out all the rotten sound barrier stuff, but left what was still dry, and it's still dry. i am not convinced that the new core is leaking...
on another note, when i was drying out the car from the original leak form the heater core, some of the sealant on the seems was dried and brittle and came up. is it possible the leak could be coming from there? the water i cleaned up this time appeared to be all clear, with no traces of prestone, so i'm thinking it's from the rain. so my next question is how can it be entering the car when the car is parked? my wife tells me it wasn't driven in the rain...
sorry so long, just trying to be clear on the details so hopefully someone can help me figure this out...

 

The low coolant level might have been just a result of some air that was still in the system. I always over fill the overflow bottle just incase there's some air in the system. The water on the floorboard could be just a leaky window seal and it puddles up down in the footwell. Mine does it sometimes but so far durring all the rain we've had here, it's been bone dry.

 

since you said its clear water you most likely have a leak from the window or t-tops..

 

take your finger and touch the water, then taste it.. I know it sounds gross, but if it has a sweet sugary taste to it, its antifreeze if not, its water. Might help you clear up a few things