Water in cab

[Unkle Fester]

I have a '98 GMC Sierra 1500 xcab 4x4, I picked it up a few weeks ago to replace my '90 burban 4x4. I've had a chronic problem of water leaking into the cab. When I first found the issue, I had to pull the seats and remove the carpet to get it dry. After finding and fixing a couple of possible culprits it happened again. Pulled up the carpet to dry on the passenger side and during a heavy rain (it constantly rains here at times, just not real heavy) I caught water running down the bare floor board. Crawling under the dash and looking, it is coming in through the recirc vent flap.

I loosened the cowl to stick a scope in, no debris seen so nothing seems to be blocking the drain, went up through the drain behind the coolant resivoir, it's clear, and the condensate drain is clear (and drips when the AC is on). I checked the hood to cowl seal and it seems ok.

Is there something I'm missing? Anyone have this happen?

I knew this was going to be a project and so far it's been fun. But this is really getting annoying.