1993 F 150 water leak passenger side firewall

Had this problem. Things/places to check are: cowl drain not open to let water out. Leaves/blowing stuff can clog the cowl drain letting water back up and seep into the interior(wasn't my problem). Unlikely but possible is the antenna lead-in might not be sealed tightly. Heater core can be leaking. My water leakage problem was because of a faulty window glass seal. I had the windshield replaced. About a year or so after that, I began noticing a leak after a heavy rain. Window guy did all kinds of tests, but couldn't duplicate/find the problem. Finally I got fed up enough and ran a bead of clear silicone around the outside band of the windows trim.....hasn't leak in 6yrs since!

Make sure you dry-out the floorboard where the water goes. This is a place that will rust easily/quickly.

Maybe your problem is one of those.....

Dave S(Texas)

thanks Dave for the very helpful suggestions. Much appreciated.