F250 Lariat. I have a pretty major leak showing up on the front passenger floor underneath the floor mat and carpet. No sign of water on top of the mat or carpet. The underneath is soaked in the low area of the floorboard. This time it ran into the door sill channel.

This leak has only happened twice since I’ve had the truck (6 years) and I’m pretty confident of that as I regularly remove the floor mats to clean and blow the carpet off with an air hose. The first occurrence was back in August ‘23 when the truck sat through a direct hit from hurricane Idalia and took heavy rain and wind for several hours. I haven’t got the leak to replicate again until yesterday when we had a full on toad strangler for almost 45 minutes. The truck has been through plenty of heavy rain events and washes in the months since the first occurrence with no problems as I check it regularly.

I feel like it has to be coming from the cowl or firewall area but cannot see where it is running down. I don’t see any signs of water from above. I know the A/C drain has been an issue but don’t think it is in this case. Yes it has a moonroof and I have had a drain issue when the truck was nearly new but no problems since. I’ve ruled that out. No cab lights.

I’ve read pretty much every leak thread posted on this forum in the last four years when they come up and read some I’ve searched. Seems there have been leaks from lots of different areas. Appreciate any leads on this one.

 

Couple related threads to help you start looking.. both these threads are simular and have different solutions. Good luck!

https://www.ford-trucks.com/forums/1...-location.html

https://www.ford-trucks.com/forums/1...raining-2.html

 

Thanks for the links, I did check them and there was one thread that was similar.

I did locate the hole mentioned, took a minute with the darker color of my truck. It was the right side where firewall meets fender. It did have some crud in it which I cleaned out, no water though. I ran some trimmer string into it but didn’t see it appear anywhere. Looks like this hole may be a drain for the wiper/cowl area?

I suppose if water backed up in that area it could find its way other places but as the poster of that thread mentioned I couldn’t figure how it was getting into the cab either and may never (hopefully won’t have to). Hopefully this got it fixed.

It’s supposed to rain this weekend so that should tell. I may run it through a car wash just to see in the meantime. I’m not planning to put the carpet or trim back in place until after both and no water! Taking a while to get it dried out properly.

 

If that doesn't work I would double check the ac drain.. in any case good luck.