Good Morning
I have a 1991 E250 that gets a wet floor under the carpet on the passenger side only, when I wash her or a bit of rain. I have been told there are drain cowls, under the removable cowl but I am not sure where they are located and how to get at them (if this could actually be the cause of my wet floor)
Any info would be appreciated
Cheers

 

Your symptoms strongly suggest a windshield leak----I'm in the glass biz and kinda know from experience in this. Because the floor is wet under the carpet its a higher likelihood that's the source of your leak.

If you pull the carpeting away from the side kick panel and look upward towards the underside of the dash you might see tracks where the leak has been running. Same with the area just under the heater core housing---if leaks are from the windshield you'll see evidence of it there too

I personally haven't seen the cowl area leaking into the cabin interior, many claim there's nothing else it could be though. That whole area is one or two pieces of steel stamped to form the firewall and wiper system components.

Without being there in person to see all this for myself its a tough call--begin as I suggest and we'll go from there.

HTH