Mystery leak under dash.

[Shiny]

I have a mystery leak under my dash on drivers side. I haven't been able to track it down yet. I have sealed the cowl screws on the drivers side so far. It did not help. The leak starts up under the dash and runs along the door bottom.
The truck is a 1999 ccsb.

 

[88GMCtruck]

I had this same problem, It's either a bad windshield install or the sealant at the cab-cowl is bad.

Here is the post of my repair.

http://www.gmt400.com/posts/867784/

 

[Shiny]

Great info! I'm going to start going after this problem here first. Do you have to remove the fenders to get that far down? Or the hood? Reason being is I will be working solo.

 

[88GMCtruck]

you could try without but it was definitely easier off.