i have a 2005 mustang. several months ago i noticed a musty smell inside the cabin. then, i noticed a wet spot in the carpet on the passenger side. several weeks ago, after a hard rain i had a lot of water on the passenger side floor.
after checking forums on the internet i started looking for a unsealed grommet or something in the engine compartment. i didnt see anything. i removed the left side of the louvered black plastc cowl at the bottom of the windshield. this covers a trough that had the cabin air filter in it.
at the bottom of this trough, there was a rubber boot that was meant to drain away the rain water that went into the trough. the boot was supposed to sit flush with the bottom of the trough but it had risen up was about an inch or two. this was stopping the water from draining and the water was going through the cabin filter and entering the car.
the filter was all black from mildew and stunk.
so i cleaned out the dirt from the bottom of the trough, pushed the drain boot down flush again and ordered a new cabin filter. i had a micronair filter FD05151P in it so i ordered a new one from them online.
looking at all the dirt, small leaves, etc in the trough made me realize that these boots need to be cleaned out periodically to keep them working properly. there are two. one on each side of the firewall and are easily reached and cleaned.
this was a very easy, quick solution and i hope it might help someone else with a similar problem.
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