Mysterious water leak

[fireball1800]

Well, I have a bit of a issue with water leaks in a new 1500 ltz z71.   The history is, we keep it garaged most of the time so water leaks had not been an issue..  recently we had to do some remodel at the house and used the garage to store/cut wood.  We've left the vehicle outside for several months.  I kept noticing that we would get an occasional moisture in the windows as the temperature changed plus a slight odor of musk smell.  Well, on a last year, we got a chip in the windshield that had to be replaced.  Then after several torrential rains over several months, I noticed one day that my drivers side carpet was soaked.  the water went all the way up the firewall. in the padding under the carpet.  Naturally we suspected the windshield and had the company that warranty it come back and fix.  after drying the carpet out with a small fan over several days. During the next rain (torrential) it was wet again.  Again we called the windshield company and they removed / reinstalled the windshield again (3rd time) .  This time while the windshield tech had the windshield removed I looked at what possibly could leak and where it would go down the inside firewall.  There was only one way and it had to be due to lack of enough windshield adhesive in the upper left corner where the water could drip into the A pillar and down to behind the speaker then into the cab.   While the windshield was out, I removed the A pillar trim so I can verify the windshield and also verify that the upper sat antenna wasn't leaking.   Again I dried the carpet and parked the truck going down hill nose down.  I took the water hose and flooded the areas we thought was leaking....  no water leaks.  ok good.  Just to double check that I didn't have another issue, I then proceeded to run water over the driver door seal area.. (I had removed the drivers sill molding and placed paper towels around the door seal bottom so I could see if it leaked) front door was not leaking.  I then decided to "just for grins" check the rear.  I took off the sill molding and noticed the carpet and the padding was wet back there.. I dried up the puddles of water, then tested the back door seal using same method.  no leak. 

 

ok then I thought where in the heck would this water be coming from.  After googling and watching a video of the rear body vent leaks, I decided to test the rear body vent on drivers side... by just letting water drip from the rear window down on the vent, and after a few minutes water started poring into the rear.   Ah ha.. So this is where it is leaking...  and it makes sense now, I have a bed cover and every time it rains water goes forward onto the cab and then drips onto the vent, the water penetrates runs under the carpet all the way to the drivers side if the truck is parked nose down.  the carpet is wicking up the water that is why it is wet all the way up the firewall.    

 

Anyone owning a Chevrolet pickup needs to verify the rear carpet is not getting wet.  Faulty or leaking vents could allow exhaust or other gases to penetrate into the vehicle as well as water.  It would be so simple to put some sort of "outer water shield" over the outside of those flaps so water could not hit the flaps. This would direct the water downward and still allow the cab to breathe..  on installation seal the unit with silicone around the perimeter where it meets the cab metal so there would be a good seal on the unit.   geez..  

 

This needs to be a recall.. this is a faulty design and needs to be redesigned.  I am taking this to the stealer next week as the vehicle is under warranty for 500 more miles.

[2018GMC]

Can you post some pics of the rear vents that leak? You may have to reply with 1 pic multiple times to avoid the size limit.

[17TXLTZ]

See the link below...I had the same issue on my 2015 Sierra about 2,000 miles out of warranty and GM refused to fix it...wanted about $1,000 to repair it. I ended up trading in the truck due to continuous issues with it.

 

http://sandyblogs.com/techlink/?p=4938

[2018GMC]

I’ll have to keep an eye out for this after the car wash or a rainy day. Hopefully GM is sealing trucks better. That should not happen in this day and age of auto manufacturing!

[Fullthrottletwo]

I was just installing  amp power steps and had to remove carpet on driver side to install wires and it was soaked so I checked back seats and front passenger side all were dry.  Did you ever get to the  root of the problem? I didn't check your pic  but I will after this post cause I figured I had no water in back seats. The truck is mostly garaged and I just took it to the car wash a few days ago? Also the carpet is as dry as a bone but insulation was soaked.

[Fullthrottletwo]

Those pics were helpful as that maybe where it is leaking. Thanks

[DDogg]

I had an issue with my 14 and the headliner and carpet being wet on the drivers side.  I had just had the windshield replaced so I took it back and the tech had it for the afternoon and noticed a few things.  He said it was quite common with chevys: the hose coming off the drip tray on the sunroof had come loose and was leaking from there.  It had been a heavy slush/snow when I first noticed it so as it melted it had filled up the drip tray. Not sure if that applies but something to check maybe?

[Lsgun1]

1 hour ago, DDogg said:

I had an issue with my 14 and the headliner and carpet being wet on the drivers side.  I had just had the windshield replaced so I took it back and the tech had it for the afternoon and noticed a few things.  He said it was quite common with chevys: the hose coming off the drip tray on the sunroof had come loose and was leaking from there.  It had been a heavy slush/snow when I first noticed it so as it melted it had filled up the drip tray. Not sure if that applies but something to check maybe?

 

Sunroof drain tubes come detached and clogged on anything with a sunroof, not just chevys. I avoid sunroofs at all costs personally.

[Fullthrottletwo]

I got my truck back after 4 days of them trying to find it. It turned out to be  the flap behind cab  there are 2 . One behind driver and one behind passenger side, mine was driver side. At first they thought it was the window. I had the tech show me. He said they have since Improved the design. It was still under warranty. 

[Gary Fernandes]

Hello everyone. 

I am only joining to post this solution as I am sure there are some people with the same problem.

2007 Yukon.  The front fender/hinge and insulator is common to millions of GM trucks.

 

I have found a solution.  Like you I have scoured the internet, and asked around, and tried all the door seals every fix failed.

I removed the cowl.  When I peered down with a very bright flashlight in the outermost corner behind the hinge, I noted that the left rear fender insulator had slipped down.  When it slides down it opens a huge gap and acts like a soup spoon.  It catches all of the water from the windshield and directs it INSIDE the insulator, instead of over the outside of it.

The water in huge quantities builds up on the inside of the insulator and is directed through the wiring harness opening.  IF this is the case with your vehicle you will note than when you dry out the floor mat, and it is kept peeled back.  Then when it rains the footwell will become soaked all the way up toward the centre console.  The jute acts as a

sponge and further confuses the source.  In my case the source was behind the body control module. 

An easy way to check if this is the problem, without removing the cowl.

Open the drivers door and look at the insulator behind the hinge.  Grab a screwdriver and attempt to push the insulator upward.  If it slides up easily it will slip back down again when you go over a bump.  The adhesive has dried out.  My leaking problem appeared suddenly without any long history of wetness.

 

I put some silicone from a caulk gun and a rubber hose extension and sealed all around the top and side of the insulator.  It was tricky with a screwdriver and a broken paint-stick but I smoothed it out reasonably.

I really hope this helps anyone with this issue.  Here is a link to the schematic.  Part #5  I would post a couple of pics but can't figure out how to.  Ha.

 

https://www.tubmangmpartsdepot.ca/a/GMC_2007_Yukon-Denali-Sport-Utility-62L-Vortec-V8-AT-AWD/_51505_5997960/FENDER--COMPONENTS-Escalade-Tahoe-base--luxury-premium--platinum-wo-Z71-wZ71-Yukon/GC07140.html

 

Good Luck   BTW there is no reason to remove the cowl cover to have a look.  Just remove the corner piece near the hinge and you can peer down there and wiggle a screwdriver to see if the fender insulator has slipped down and is gaping open.

 

Gary

Edited October 21, 2019 by Gary Fernandes