Water leaks under the dash

DanL · October 27, 2016

Well the dealer has now had my 2016 Sierra Denali 2500HD diesel for 4 1/2 days after I found my passenger front floor saturated after some heavy rain. My first thought was evaporator drain. They said that wasn't it. They sent it to a window shop to check all seals and the moon roof. Negative. They brought it back to the dealership and put it under a "shower". No leaks found. Then they asked me if I may have left the window open. I won't repeat my reply. I told them I wanted them to re-check the firewall openings, etc. An hour later they called and said the leak had been found! It was a bad weld in the r/s wheel well letting water in. Now, they said, it turns into a body shop issue and they were about to call GM for authorization.

We'll see. At least they gave me a loaner for the duration!

DanL · November 13, 2016

Well I'm now in the 4th week that the dealer has had the truck. They've reported to me that the leak was from a broken weld in the passenger front wheel well, then they said it was from a broken weld in the windshield wiper compartment, then they said neither one of these was the source. A week ago they said the entire passenger compartment had been stripped-seats, dash, carpet, etc. Last Thursday (Nov. 10th) they called and said they determined the source of the leak really was from the windshield wiper compartment. They are hoping to have it put back together by this coming Monday or Tuesday. This will be 28 days with my truck. Needless to say, I'm not too impressed with the dealerships diagnostic team and, for that matter, the entire service and body shop departments. We will see during the next rain how they did.

cbrsilv15 · November 14, 2016

Keep us informed!

pm26 · November 15, 2016

So here's a update. Under ther cowl there is a water diverter piece. Well on all the welds on the truck they use seem sealer. On the weld by this piece the seem sealer was put on and a extra piece remained as the robot or human that applies the seem sealer and stopped the application extra leaked out and was left on the cowl where the water diverter lays flush. Well because of the extra sealer under the water diverter it was not flush and the water ran under the diverter and down the firewall and in though where the wiring harness is on the passanger side. The had to move the fender out of the way to repair it correctly. The removed the extra sealer and made the water diverter flush then sealed the water diverter and re assembled what they removed. No more leaks and they dries out the carpet and insulation stuff and I get to pick it up tomorrow. We shall see how they did when I inspect it tomorrow. Thanks for the replies.

They probably use "seem sealer" instead of "seam sealer". It only seems like a sealer!

Pacfanweb · November 18, 2016

R/F floor is probably coming in around the wiring harness behind the fender.

I have seen several like this.

creep · January 27, 2017

One month out of warranty and I get this same problem. Just dropped it off at the dealership to have a water leak specialist check it out tomorrow. Its going to cost me $110 just to have it looked at. Why do I feel like this is going to hurt...A LOT? The lady that checked me in said it was probably the roof fin before I even said where it was showing up. After I told her it was under the dash by the e-brake she said it could be under the cowl. These are not normal wear-and-tear breakdowns. These are defective parts or manufacturing defects.

Pacfanweb · January 27, 2017

One month out of warranty and I get this same problem. Just dropped it off at the dealership to have a water leak specialist check it out tomorrow. Its going to cost me $110 just to have it looked at. Why do I feel like this is going to hurt...A LOT? The lady that checked me in said it was probably the roof fin before I even said where it was showing up. After I told her it was under the dash by the e-brake she said it could be under the cowl. These are not normal wear-and-tear breakdowns. These are defective parts or manufacturing defects.

That location could still be the antenna, although it's slightly unusual you've not seen water above as well.

creep · January 28, 2017

I got mine fixed today. They said it was the roof fin leaking. It cost me $180 to have it fixed. Not nearly as bad as I thought it would be but it still sucks that I had to pay for what is pretty much a design flaw.

5001riverbed · March 24, 2017

I have a 2014 Silverado LT. Started seeing water puddling in the floor mat on the driver side near the parking brake. Took it to the dealer and it turns out....surprise, surprise.....the high frequency antenna on the roof is leaking. It is sounding like this is a well known problem to GM, but for whatever reason they will not acknowledge that is a persistent problem.

My AC started blowing warm air about a week ago, so I had them check that too. Turns out there was absolutely NO freon left in the system. After recharging and pressure testing, they found NO leaks. I am no physicist, but it is my understanding if there is a substance in a sealed system and it disappears then it must have leaked out.

I have a sick feeling this won't be my last visit to the shop with AC issues.

Jim Fulton · November 19, 2017

My 2015 2500 hd has been in 6xs for water. 3 fins replaced , 2 sun roof seals . Passenger fender removed to seal fire wall, Full carpet replaced because of mold. Rain started again so, Now its time to go back again. floors wet water dripping from the roof again. Headliner shot and water stained. Not a happy camper.... Oh cant go camping truck will be back in the shop again.

xps800doo · February 18, 2018

Wow totally sick to my stomach reading this post, just purchased a used 2015 Sierra 2500 with 60,000. Low and behold I have wet carpets under all 4 feet locations... this is not a daily driver and has been parked for 2 weeks now!!! Bought it out of state from a dealer 6 hours away...all these repairs sound expensive!! So disappointed,disgusted,heart broke,sick.... guess I’ll have to call my local dealer Monday...

Sent from my iPhone using Tapatalk

Thomas An · February 27, 2018

I have the same issue but truck won't start due to short in fuse box that cause battery to completely die.

gpd387 · April 7, 2018

On 5/17/2015 at 8:16 PM, GMCustomerService said:

Hi Collimare,

We're very sorry to hear you were experiencing water penetration in your new 2015 2500 Duramax. It's good the dealer was able to address this for you. If you need any further assistance or have any questions, please don't hesitate to send us a PM. We're here if you need us and will be on the lookout for updates.

Sincerely,

Eddie A.

GM Customer Care

GM,

I have a 2015 2500 Duramax (High Country) and have noticed a musty smell. With all of the rain and snow, we have been getting in WV I have not been able to open the windows and air it out. Yesterday I removed the drivers' side factory may and the carpet is soaking wet. IS there a service bulletin on this? I spent A LOT of money on this truck and would like to see a little return on my investment.

Hdwrguy · December 18, 2018

On 3/24/2017 at 2:27 PM, 5001riverbed said:

I have a 2014 Silverado LT. Started seeing water puddling in the floor mat on the driver side near the parking brake. Took it to the dealer and it turns out....surprise, surprise.....the high frequency antenna on the roof is leaking. It is sounding like this is a well known problem to GM, but for whatever reason they will not acknowledge that is a persistent problem.

My AC started blowing warm air about a week ago, so I had them check that too. Turns out there was absolutely NO freon left in the system. After recharging and pressure testing, they found NO leaks. I am no physicist, but it is my understanding if there is a substance in a sealed system and it disappears then it must have leaked out.

I have a sick feeling this won't be my last visit to the shop with AC issues.

I am currently seeing the exact thing on my 2014 Z71 crew cab truck. I love my truck, but the dealer has had it for four business days and says they cannot see a leak. I am going to have them check the antenna on the roof. God, I hope that is all it is and that there is no other damage inside the roof. I am sick and angry at the same time. This should have been found before the truck even showed up on the dealer lot.

Hdwrguy · September 2, 2019

Guys, just an update on this issue. To recap my issue was ,with heavy rain, water was dripping down and would puddle under the dash just above the parking break area. After two unsuccessful visits to the dealer, I decided to work on this myself. On the satellite radio antenna a.k.a. shark fin antenna, if you look at the base on this antenna, in the back there is a small rectangular open slot. The water was coming in there.

So I started to think to myself why it never leaked when it was new. About 18 months ago, I had a leveling lift kit installed. My theory is that this somehow changed the dynamics of the truck and water would enter in this slot easier.

The fix was very low tech. Placed painters tape around the base of the antenna and then put a bead of high quality clear silicone around the entire antenna and made sure that the slot in the back was also covered.

It has been a couple months now with heavy rains and absolutely zero leaks.

I hope this helps.