Ive got a 99 F250 (5.4 if that matters), after a good long rain like the one we had this weekend, when I drive the truck I get water splashed on the passenger floorboard. It hold enough water that if I rock the truck side to side I can hear it sloshing. Im wondering if there is a common drain for these things that gets clogged. When my a/c runs I get a nice puddle under the truck so it looks like that is not clogged up, and I didn't know if they were the same drain or not. Anyway, thanks in advance for the help.

 

Re read the problem, which rules out moon roof...

 

Yup, no moon roof.

 

Anybody have any ideas on this thing?

 

Several others had similar water leak problem (including myself). Not A/C drain and not radiator fluid , only happens after a good rain.

I blew cowl area with compressed air (without removing the cowl covers) ,quite a bit dirt blew out . Then saw some cracks around cowl screws , patched them with epoxy . Did not help .

I did not have a chance to try to isolate the problem with a hose . I would like to hose just the cowl grills (making sure no water going to lower windshield seal ), do I have a leak ?
Then hose lower windshield seal area (check again) , then hose upper windshield seal and door seals .

Let us know if you find out a solution. Good luck .

 

Had another good rain this passed weekend, filled the truck up with water again lol. I might try to focus some time on it this coming weekend and try to sort this crap out.

 

I had a car that did this... a small hole was made by rust...in the cowl corner. near fender.

 

Well, I didn't get to spend any time on it but this week is supposed to be really wet in my area. Ill have to get out the blow dryer and dry the carpet up.

 

Water from the cowl area should simply be directed to each side where it drains into the fender area. This area is too large to clog up.
The first thing I'd do is ensure the rubber gasket strip across the top of the firewall is in place, then I'd look for the route to the blower.
I had a Grand Prix that allowed water in through the blower because the firewall gasket was knocked off, and I'm confident that rain water is somehow getting to your blower motor too.

 

I just this week solved the mystery of my water intrusion. SHORT VERSION- The cown drains were clogged so in heavy rain the cowl filled and overran into the cab.
FULL VERSION- A few months ago my horn sounded on its own, and wouldn't quit. A mechanic said it was caused by the BCM (body control module which apparently is also know as the General Electric module (or GEM). But the horn didn't blare while there and the mechanic didn't see any signs of water intrusion so we just left it alone for the time. The two weeks ago I had electrical gremlins draining my batteries and frying the alternator (there was a 1/2 amp drain due to shorted electronics). So now it is time to replace the BCM but was told it has to be programmed by the dealer. So I went to the dealer who of course said they need to do an evaluation before making any repairs, and diagnosed a leaking windshield. Replaced the windshield and that was not the issue. Back to dealer and told them to actually look to find the cause, not just guess. I suggested a few possibilities after reading these forums and all were promptly dismissed. When they pulled off the cowl and looked inside they found the cowl drains on both sides were clogged. Cleaned them out and now it drains fine.
Finally I can proceed with having the repairs done and stop disconnecting both batteries every time I park the truck. (Now I just need to convince the dealer to reduce their labor charge by 2 hours to offset the cost of the unnecessary new windshield.)
Good luck solving your leak. Hope this helps!

 

Man, I forgot about this thread. Not that it matter though as I havent been able to do anything with the truck. Ive been using it only when needed and its been parked most of the time. I will definitely follow your lead and pull that cowl off.

 

I am having somewhat of the same problem.
2004 f250 superduty