I understand that there can be a problem if drains below windshield get plugged. Water can come in through the filter that primarily affects the passenger side of a 2005 - 2009 mustang. That is not what is happening to me. Both drains are unplugged. I just bought the car so i am not sure if the previous owner unplugged them or not. My problem is on the driver side. The carpet and pad under the matt is wet and deteriorated. It looks like its been happening for a while. Is there a common problem with water on the driver side that anyone has experienced. Any good methods for determining where the water is coming from?

 

It can leak in numerous places, do a search for TSB 08-26-7 and it'll show you where.

 

I just added a few pics of trouble spots in the last couple posts here-> https://themustangsource.com/forums/...469258/index5/

 

Leaks are most commonly known on the drivers side to come from a leaky firewall or more commonly convertible tops, do you have a convertible? If not than I'd pull up the carpet on that side and look for rust/cracks/holes/ unsealed line holes and maybe even check the lower front corner of the door. How does water run down it when you spray it with a hose, if it pools up in the crack or seams like it goes in than its probably squeezing through crack on the plastic and down into the carpet. It's just the drivers side right? Hopefully that'll help you a little for finding it, but good luck once you do, I hate wet floors. Intolerable in my book.