Condensation/dampness passenger area under dash but no active water leak

[drag sgt]

I made a discussion on the GMT400 forum but thought I'd cross post here, as well as I'm mostly worried about moisture near the ECU

You can see my full images here but the short of it is that I'm getting a mildewy smell up front on the passenger side now that the weather is wet/humid, but am not seeing active water intrusion; only condensation building up. All the drains are clean and no cracked body seams, but I am going to silicone the screws as a precaution. I wonder if the condensation might be more of an indicator of an air gap in the windshield seal.

 

[Paveltolz]

You might want to check the windshield seal for signs of deformity, age etc. causing leakage around the sides and bottom. Difficult to ascertain but, its possible. Leaks at the tops running inside would be visible inside the glass (current issue of my own).

The further up the firewall the carpet is damp would help isolate the source coming down from above or up from below through a compromised body plug in the floor panel as they rot out far quicker than the actual floor..

 

[dbrannon79]

I had a leak in the same area on my truck, only later to find out even the headliner around the passenger side sun visor was getting wet. later I discovered the rear brake light seal was cracked. water was traveling all the way up and down to the front passenger area on my crew cab!

if not, I'm with Paveltolz, you can use black RTV in and around the windshield and be able to hide it. also under the wiper plastic cowl where the cab has seam sealer. look it over good. it can be something as simple as a self tapper holding something on the firewall under the hood in the wrong place too!

another place to look too is under the carpet for drain plugs. driving on wet roads and moisture gets in, evaporates into the rest of the cab.

 

[MrMarty51]

For Me, if it would be a compromised windshield body flange and the rest of the body is in good condition, remove the glass, make the repairs and install a new glass.

 

[SnowDrift]

Spray foaming glass cleaner around the outside perimeter of the glass and then blow compressed air from the inside to see if any foam is affected.

 

[MrMarty51]

Spray foaming glass cleaner around the outside perimeter of the glass and then blow compressed air from the inside to see if any foam is affected.

That brings back some funny memories.
My 78 MG-B Roadster.
The windshield was bad busted. I had bought another MG-B for a few dollars. Good windshield in this one, body rusted out.
I ordered a new windshield gasket and after it got here proceeded in changing out the windshield glass.
Okay now, this was during the real late fall to mid winter months and the sun went down it got right cold.
Got off work and decided to change out the windshield.
By the time I got the frame dismantled and the glass removed the temps was getting downright cold.
Slathered that gasket real good with dish soap. And getting the glass from the rusted MG and the gasket in place the operation had taken on a difficult level.
After a few, well, quite a few, choice words and much work the car was back together and drivable.
Come spring and rain.
Ohhhh boy, drive the little orange crapper car.
One day out cruising and got caught in one of them squalls, pulled over and put the top back over the interior and fastened it down.
Then running about 65mph there began a series of bubbles between the gasket and glass and gasket and body.
You see some of them super bubbles, thats what was happening within the confines of that little car. My nephew was maybe about ten or twelve, he was along and he still talks about how funny it was riding in the “ Bubble Machine “.