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Discussion Starter · #1 ·
Been trying to figure out where a leak is coming from and I had the chance this evening to start looking.
I pulled the cowl and cowl screen,stuck a hose in there and let it run for a few minutes.

where the floor pan meets the firewall it started coming up thru the seam sealer. Is the firewall double paneled?

if it is then I have to re seam seal the wiper troth and that area inside the cab.

Water is coming thru where the silver sharpie is.

Water Automotive tire Road surface Automotive exterior Gas
 

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Discussion Starter · #3 ·
I just took another deeper look into the situation and figured it out. The seam sealer in the wiper troth gave up the ghost. It’s leaking into the engine bay below where the firewall and the troth meet.
Looks like I’ll be finishing that tube of seam sealer here shortly.

I recently re done the seams on back of the cab as it was leaking as well. I went after it before but didn’t put enough. I approached it like I was siliconeing a shower or tub with a tight clean bead. This time I got it right.

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I suspect this is a 1st Gen, but you do not specify. I am thoroughly familiar w/ 2nd Gen Cowls, Cowl Drains, and front Cab sealing at this point, but not 1st Gen. As clearly shown in my extremely verbose thread below, on the 2nd Gens, sealer failure allowing Cowl water to enter the engine bay would not contribute to leaks into the interior unless there was a secondary leak(s). My 2nd Gen daily driver Cowl has been leaking to the engine bay for a decade or so. In your case, it is possible the water is traveling behind the sealer for a significant distance. If you remove the sealer on the inside till you no longer see rust, you will likely be able to figure it out. On my daily driver 2nd Gen, the bottom of the firewall behind the R wheelhouse rotted out. The source of that leak was more obvious than yours, apparently.

Interior cab rust near front right corner (Cowl drain)
 

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Discussion Starter · #5 ·
In my last pic it was apparent the water was getting past the seam sealer in the troth as soon as I seen those 2 streams rolling down the firewall in the engine bay.
Shortly after those streams were visible the inside started seeping out.
Now I want to know how it’s traveling from the troth and getting under the seam in the interior.
 

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In my last pic it was apparent the water was getting past the seam sealer in the troth as soon as I seen those 2 streams rolling down the firewall in the engine bay.
Shortly after those streams were visible the inside started seeping out.
Now I want to know how it’s traveling from the troth and getting under the seam in the interior.
Possibly only indirectly related, as soon after you place water in the Cowl Plenum, the water will also likely be at the drains behind the fenders, if design is similar to 2nd Gen.

On 2nd Gens, AFAIK, the leaks tend to occur at the extreme R & L edges of the Cowl Plenum, in the vicinity of the drains. This is especially true at the R edge by the Air Intake Assembly.
 

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Been trying to figure out where a leak is coming from and I had the chance this evening to start looking.
I pulled the cowl and cowl screen,stuck a hose in there and let it run for a few minutes.

where the floor pan meets the firewall it started coming up thru the seam sealer. Is the firewall double paneled?

if it is then I have to re seam seal the wiper troth and that area inside the cab.

Water is coming thru where the silver sharpie is.

View attachment 367798
I would remove/pull back the plastic rubberized panel will make for a lot less guess work. Check antenna grommet is pushed into hole in firewall this cable gets pulled during petty much any major dash service. 30 year old truck dash has been out at some point.
 

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Discussion Starter · #8 ·
I figured out the issue, I had shifted the area where the panels are pinched and broke the seam sealer loose when I was putting my trans in and moving it tI cleaned, prepped and re sealed the gap and all is good now.

As soon as I get my front glass channel cleaned up I’ll get my front glass installed and determine if I need to clean up the seam sealer on the driver’s side or was it splash out front the leaking front glass.

I’m going to re seal the troth also to preserve the metal under there as well.
 

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Discussion Starter · #9 ·
For those following, I got the glass replaced, dr and pass area where the firewall meets the floor all sealed, and the troth is done.

my leaks now are where the gas pedal comes thru and the hood latch cable. After these 2 are fixed it’s carpet time.
 
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