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I have a '96 F150, 2WD, 4.9L I-6 w/ auto trans, 186,000 miles.

After a rainfall, I notice that the floor mat on the drivers side is soaking wet. The rain seems to be leaking in behind the dash or firewall onto the floor. The dash itself is dry. I looked all over the truck inside and out but can not see anything that would suggest what's wrong. Has anyone experienced something like this, or have any possible causes or cures?

Everything else on the truck works fine and there is no indication that the electronics are getting wet. The truck runs like a bear otherwise.

Thanks in advance !

 

The windshield may need to be resealed.

 

It's likely Harabingatz has the same issue I do. Read below:

1990 F150 Custom / 4x4 / 4.9 liter I6 300 / Manual Transmission

Water is coming into the cab near the ECU / computer. I posted about this awhile back and it is not the windshield. Someone mentioned that I should check the cowl drain, which I did and it was clogged. I cleaned it out, and forced water via garden hose into the cowl, which is draining well, but water is still entering the cab.

Where the water is entering the cab:
If you are facing the pedal assembly from the inside of the cab, the ECU is mounted horizontally and there is a metal mount / access plate of sorts that mounts to the left side of the wall of the cab to the left of the ECU, just above the 45 degree angle of the floor. This is where the water is entering the cab. The seal feels dry rotted, so it's likely that this is how water is getting in. My concern is, should water even get behind this metal plate? I tried to find a replacement seal on LMC with no luck.

Any ideas?!

Thanks,
Nabor J

 

Should be pretty easy to make a new watertight gasket

 

I was thinking about making a seal by using silicone. Any recommendations?

 

I am thinking now that the "rain drain" is clogged- not sure the technical term for it, but it gets clogged over the years with dirt, crud, etc... this only happens after a good soaking rain, making me think it's the culprit. Are there any ideas how to unclog it??

Is it a DIY job or perhaps a dealer job?

Thanks in advance!

 

Here is how I fixed the leak on my truck: First, locate the cowl drains on each side of the truck that fill with dirt / etc. and run a screwdriver from the bottom up to free debris. Follow this with a blast of water along the corners of the firewall from the top down (hood open). This will clean the debris, which you should see on the ground after doing this. Where the water was entering the cab in my truck: If you are facing the pedal assembly from the inside of the cab, the ECU is mounted horizontally and there is a metal mount / access plate of sorts that mounts to the left side of the wall of the cab to the left of the ECU, just above the 45 degree angle of the floor. You will need to take out the ECU which is just two 5mm bolts (access from engine compartment), then remove the plate from the inside of the truck, (4-5 bolts.) The gasket is likely bad, so just RTV a thick bead around the inside of the plate, press it back in place, and screw it back in. Put the ECU back in and let the RTV set for a day, then do a water test by blasting the windshield and top of the hood area to see if water still comes in. If not, problem fixed!