HELP! Driver's side floorboard leak

I've got an 01 Prerunner and I've noticed my driver's side floorboards are wet. It's not the AC, it's not the heater core. I've run water over the outside looking for leaks and didn't see any. The carpet is pulled up and there are 2 drain holes on the floor, and I'm wondering if anyone has ever noticed or heard of these rubber gaskets going bad or leaking?

 

You say it's not the AC, but often it is the AC drain line being clogged.

How did you determine it's not the AC?

 

Because I've checked the line. It's leaking when parked after not using AC and AC would leak on passenger side which is completely dry. The wetness is only on the drivers side.

 

Gotcha. My bad, I missed the DS comment in your original post.

 

Have you installed any wires through the firewall grommets? I ran some wires there one time and it leaked so I looked for days and finally found it.

 

No wires, and I've checked the grommets too. No leaks there. Frustrating to say the least.

 

this happened to me also.

 

I've had a leak for a while on the drivers side. I finally pulled the seat out ripped up the carpet, popped the hood and started hosing down the windshield and fire wall for a few. Then checked and found the floor wet. It was coming in through the wiring harness, following the wire bundle into the cab and then running down to the floor. I have since made the wires dip before coming into the cab and then put a bunch of kitchen/bath caulking in the seal on the firewall.

 

I had a leak on my DS as well once. I traced it back to the amp wire through the firewall grommet. I used a piece of that tarry tape that you seal a new door frame with to make a little roof over the wiring. It's worked for several years now.