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I have water coming into the cab somewhere near the top of the passenger side firewall. Hit it with water and you get a steady stream of drips coming in behind the air duct work over the passenger foot well. I do not think it is the windshield. It is not the heater core. I think it is dried out seam sealer under the cowl or a seal around one of the HVAC penetrations in the fire wall.
So, I am going to start taking things apart and hunting for problems.
Any common problem areas I should look at?
Recommendations for sealers? Seam sealers? High temperature sealers? I assume the best method is to completely remove old sealer and apply a new bead??
Don't forget to check the windshield wiper pivot while you're in there... I'm not sure if Ford had that problem, but on Mopars it was almost a guaranteed water leak!!
You can isolate the problem area with a hand held pressure sprayer (recommended) or a squirt gun as these will allow you to better focus a stream of water as compared to a garden hose.
Begin with the seam/opening closest to the bottom of the firewall. Spray a steady but low pressure stream of water on the seam, give it a minute and then check for leaks. Work your way from bottom to top in this way - once you see the water in the cab, the last area sprayed is the leak.