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Discussion Starter #21
Glad it's fixed! What a freak failure location...
Yeh, my thoughts exactly. But then I realized .... not as "freak" as it would have been if it had turned out to be that 'seal/gasket' between the heater box and firewall. After discovering the leak the second time after bringing my truck home, I went over the old seal that had been replaced with a fine toothed comb and a magnifying glass. Nowhere on the seal, either side was there any indication of a water trace. I even took a few detailed pictures for future reference if needed. It was not much more than a piece of open cell foam rubber, and as I understand is pinched in between the inner side (cabin side) of the firewall and the face side of the heater/blower box. Open cell foam is never used for a water tight seal, only an air seal. In this case it prevents the higher pressure air from the blower from escaping between the box and firewall thereby forcing it out through the duct system, and also I guess prevents any foul air from the engine bay from entering the passenger cabin. But, that foam rubber seal is pinched in between those two flat surfaces which never move. No logical reason for it to ever fail unless it is so old as to be completely rotten, dried out and crumbly. I've been told there is some kind of TSB about that very seal failing, but I've not seen nor heard of it till now. Anyone out there heard of this seal ever being an issue? I may be picturing it all wrong, but I think I'm pretty close.
 

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Guess I'm just sceptical, by nature; but those grommets are not designed to keep out water. It is my opinion that if water gets to it, it will leak.

So, from your description this point is behind the fender and part of the lower area of the A pillar; and, you check the truck after a heavy rain and the truck was parked during the rain.
My question, how did the water even get to the grommet?

I see it's only been a few hours from when you provided the update, and I expect the weather is nice.

I hope, when it rains, that I'm proven wrong.

Good luck Joe

And Joe, if it does leak, tape off the vents at the base of the windshield, use lots of duct tape, and see if that stops it.
 

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Discussion Starter #23
OK, here's where I think we are. 1st, it rained this morning and afterwards all was dry. It wasn't a real hard rain, but enough I think to have shown up if it were still leaking. Now, as to how the water gets to the grommet. The best I can tell is that all the water runoff from the windshield and the cowl vents is collected in a 'trough' at the base of the windshield and under the cowl vents, right at the very back edge of the hood. And BTW, there is a pretty substantial rubber seal under the very back edge of the hood and all the way across that prevents any of this water from entering the engine bay at the rear of the hood. That water is then channeled to either side of the truck and falls down through the opening behind the inner fender, and in between the outer fender and the truck body. If you'll visualize removing the fender, what you would see is the side of the body directly below the 'A' post and at he front of the door. Between the wheel opening at the front and the door opening at the rear. I've really looked and see no other option. I have to assume that this is fairly common for the run-off water in most vehicles, I've just never thought about it before. I'm definitely not a 'paint/body' man. But, what I don't understand is that down in that open space between the fender and the body, I can see some kind of insulation that resembles 'rock wool'. Likely some kind of sound deadener. No doubt this insulation is impervious to water, otherwise it would stay soaked and lead to a bad rust situation on the inside of the fender. As for the harness grommet not being water proof, I think the design is that the wiring harness is pulled downward at the outside of the grommet and through-hole so that any water getting on it will drain away from the truck rather than follow the harness into the truck. Since I didn't actually see the actual grommet and was only told by the tech it had cracked/split, leads me to believe that when it cracked it allowed the harness to follow it's natural direction while under bend tension and to rearrange itself to an upward direction just enough to allow the water to flow into the truck instead of away from it. It wouldn't take much of a change in how that wire bundle lays. That would would explain why it (the leak) started all of a sudden. It's a hell of a chunk of wire (about an inch+ in diameter) in that harness and a pretty small area to be bent to control the direction it lays. I'm totally amazed at the design of the water flow from the windshield and cowl vents being directed down through the opening between the fender and the truck body, but after thinking about it, I don't know where else it could be channeled. There's just enough room between the battery and the fender to look down through that opening to see where the water is supposed to flow, and with a good flashlight it can be seen. I'd appreciate anyone who has a similar truck to look at theirs and see if they agree with my description. I'll be checking back from time to time till midnight tonight ..... after that the cable company is taking down our I-net service for some kind of maintenance. Won't be back up till early hours of the morning, but I'll be back again after that.

thanks and regards,
jumpinjoe
 
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