Water in cab
 

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.

Re: Water in cab
 

Welcome to the board! I guess you are on the west side of the Cascades, right? Anyway, I know you guys get some rain....a lot of rain. I can sympathize with you, today.

Chevy Tech has a lot of expertise in these trucks and can probably steer you in the right direction. If the question was about a '67-72, I could jump in and steer you around, but you probably already know about those trucks. Sounds like you have checked the obvious. What about waiting until a dry day and then get a hose and a friend. I would flood any suspicious area with water while the extra pair of eyes watch and look for seepage. You'll have to be mindful of the areas of concern, and hope that you can duplicate the problem.

Again, welcome to the board!

Re: Water in cab
 

I had a few different areas that were suspect on mine. One was the door seal on the drivers side, there is a rain/wind guard above the seal and it was hanging down and letting in rain. There is also screws in the cowl area (under the wiper arms) that need to be removed and have silicone put on them and run back in. This is more common to these trucks and will let rain in at the firewall.

Edit: There is a sticky post on the FullSizeChevy.com forums that talks about leaks on the NBS trucks, but there is info on the OBS trucks like ours mixed in. I would post a link for you but there site is down or too busy to get on right now.

Re: Water in cab
 

X2 on the cowl panel screws. Also check to see if there are any extra screw holes over the fresh air intake area, & if you remove the cowl cover make sure the seam around the metal patch over the fresh air intake is sealed good(this is on the far right just under the cowl cover). I would recommend using a good body & seam sealer like 3m ultrapro urethane seam sealer.

Re: Water in cab
 

Cowl Screws, got it. That one should be an easy one... if the rain lets up for more than 5 minutes. Never knew there was a patch under there either.

Easy first step.

Re: Water in cab
 

The patch is a factory installed piece, only ran into 1 that was bad, never hurts to check.

Re: Water in cab
 

Hmm, I have suspicions that the truck was in an accident and never reported (carfax and DMV records are clean) That could have caused the patch to come unsealed.

A lot of the front end looks new, the framework around the radiator is new, the fender wells too.

OK, I know what I'm doing tomorrow evening. Hope it works

Re: Water in cab
 

Well, I think that worked. I found a missing screw and sealed all the screws then let the sealant cure. I ran the hose over the cowl for 15 minutes and no water entered the cab. Of course the proof is in the pudding. It's raining today (big surprise) and when I get back out to my truck should show if this worked.

Big thanks to bwood and truckpoorpackrat, this is one to remember, great lesson on a water leak from a source I never would have thought of.

Re: Water in cab
 

Wow! Another satisfied customer. Glad you got it fixed.

Re: Water in cab
 

Glad to help. I went round and round with this for about two months last year. Keep us updated.

Re: Water in cab
 

OK, it rained pretty hard (we seem to be getting a lot of that) and water still came in. I pulled the cowl and noticed how the screws were mounted and sealing them shouldn't be an issue (except the one over the air intake) Looking down into the fresh air intake side, I found mud and dirt had accumulated right up to the top of the fresh air intake dam. So I flushed it out (mopped up the water inside) and put it back together. Ran the hose for a few and water still came in.

So I threw my hands in the air, figuring I need to pull the plate over the intake and seal around the intake dam real good. (sounded like the easiest fix) But two days later it rained the hardest I've seen in a long time and no water came in. I'm thinking with the hose I sprayed water over the intake dam.

I still need to see if I have to seal around the dam, but it's a new direction and a pretty firm target I hope.

Again, thanks for the help.