GMC Sierra 1500 water leak problems

Filed Aug 19, 2026 · NC

The GMC Sierra has a known issue from the manufacturer in which the power sliding rear window can start to leak water into the cab of the truck during rain or other impact with outside water. This issue allows water into the cab through a cracked or faulty seal, which impacts visibility and allows water to penetrate inside, producing risk for moisture to collect on the back window and potentially cause mold to grow inside, further creating a health risk. Further, the water intrusion can lead to interior damage, as well as potentially cause electrical failure and unsafe operation. This is a known issue dating back to January 2019 when GM issued Technical Service Bulletin 18-NA-383 and has continued to be revised since. The component has been reviewed and inspected by the dealer and is known to the manufacturer; however, they are unwilling to fix without cost as this is not a recall.

Filed Jun 28, 2026 · Body · MA

There is a water leak in the rear passenger compartment of my vehicle. Unsure where water is coming from. Continued leaking poses a risk to my safety as I may be exposed to black mold as well as anyone else who is riding in my vehicle. The problem hasn’t been addressed by the dealer yet but this is a known issue. At this point I have spoken with a representative from the service department at the dealership but cannot get an appointment for several weeks. I was also advised that the problem would need to be diagnosed before being addressed at my cost due to being outside of the warranty period. There were no warning lights or any other signs that this is occurring and was only discovered because I was putting something in the back seat on 6/26/26.

Filed Jun 11, 2026 · Body, Electrical · GA

The plastic upper rail glass guide frame on the rear sliding window assembly of my 2023 GMC Sierra developed structural micro-cracks during normal vehicle operation. This manufacturing defect is a known issue tracked internally by the manufacturer under Technical Service Bulletin (TSB) #18-NA-383.This structural failure allows severe water intrusion into the passenger cabin. The leaking water runs straight down the inside back wall of the cab, completely flooding and corroding sensitive, factory-installed electronic safety modules mounted directly beneath the leak path.This continuous water intrusion caused the catastrophic electrical failure and corrosion of the video processing control module located behind the rear seat. The sudden failure of this module completely disabled the rearview digital mirror camera and the 360-degree perimeter driver assistance cameras, creating immediate blind spots and an active driving safety hazard while operating the vehicle.The vehicle was inspected and repaired by an authorized dealership, confirming the rear window leak as the direct cause of the electronic destruction. The out-of-pocket cost to replace the water-damaged safety components was $2,747.00. Because the manufacturer refused to cover the replacement of the defective rear glass assembly, the structural leak remains unresolved. This active water intrusion continues to flood the cabin, creating a health hazard via mold growth and guaranteeing that the newly replaced safety cameras will inevitably short-circuit and fail again.

Filed May 30, 2026 · TX

Back window water leaking causing bad smell and mod

Filed Dec 6, 2025 · CA

Experience water leaking 3rd brake light and rear window. Leaking in both areas. Also concerned about mold that could be caused by this.

Filed Aug 13, 2025 · Electrical, Engine · GA

Subject: Urgent Vehicle Safety Complaint – 2019 GMC Sierra Denali Escalating mechanical and electrical failures — many beginning before 100,000 miles, and continuing as of today, at approximately 110,000 miles. These issues have made the vehicle unreliable and unsafe to drive. Since purchasing the vehicle, I have had it serviced regularly and reported that it was driving rough, jerking into gear, and showing early signs of engine and transmission problems. These issues were noted during multiple multipoint inspection services, yet no lasting solutions were provided. Major issues have included: •Engine performance failures •Fuel injector malfunction •Serpentine belt and idler pulley damage •A/C compressor belt failure •Power steering malfunctions •Vehicle stalling at traffic lights •Loss of power on major highways •Rear window water leaks •Significant and ongoing electrical system problems •Shaking when brakes applied after having brakes and rotors replace in March •Screen monitor going out after paying over $ 900 dollars for updated software and repairs to the electronic component that cost over $2500. Despite continued maintenance, on Thursday, July 3, 2025, my truck began losing power and smoking heavily while driving on a busy highway in Georgia. My grandchild, who was riding with me, yelled, “Grandma, it’s smoking — please get out!” as we pulled off the road in fear of a fire. This terrifying incident left us stranded and emphasized just how dangerous this vehicle has become. I filed a formal complaint with the GMC Corporate Office, but no support provided or an investigation. Over the past six months, I have spent more than $5,000 trying to keep this vehicle operational. So many critical systems have failed, despite consistent maintenance, raises serious concerns. Finally, the fuel injector repaired 3 days later a message on dashboard displaying service Tire monitor system and steering wheel shaking when brakes are applied.

Filed Jun 18, 2025 · Visibility · CA

The rear back glass is leaking water excessively in to the inside of the vehicle when it rains or gets washed. The vehicle is available at any time for inspection. The amount of condensation that accumulates on all the interior windows makes it impossible to see out of the vehicle. The defrost can not handle the amount of moisture build up. The Dealer knows about this condition and it has been verified by a window company. The manufacture knows and understands there is a problem and has put out a Technical Service Bulletin ( TSB 18‑NA‑383 ) for this issue but will not cover the repairs. GM knows that every single vehicle with this window designs from 2019-20121 will leak just outside the 3 year 36k mile warranty coverage. The cost of repair is approximately $2k. Dealer will not cover repair.

Filed Apr 27, 2025 · Body, Electrical · WI

Rear sliding glass window is leaking water around the exterior frame. This is addressed in TSB 18-NA-383 but not covered under any warranty. My rear seats and carpet are becoming wet. I am concerned about the possibility of mold and an electrical short/fire resulting from water intrusion. There are many reports and discussions on the internet regarding this issue. Full window replacement estimated at $1300. Patchwork repair with caulk is estimated at $600 with no guarantees of success. I would expect GMC to cover the replacement of the rear glass in kind and remedy any other damage to my vehicle due to water intrusion into the cabin area.

Filed Apr 22, 2025 · Body · FL

Had water leaking into cab of truck. First incident they stated it was a rear window seal and it was "repaired" under warranty. Second incident I was advised it was body panel separation where the cab roof and side body seam was leaking. It was repaired by sealing with "body seam sealer." I later read these repairs should have been welded. This was after the warranty expired and I had to pay for it. I then read on the Silverado/Sierra forum this repair should have been a weld not just "glued" is this a safety issue?

Filed Feb 1, 2025 · TX

Water entering from the rear window causing rear seats and roof hard cover to get wet and cause a wet odor (humid). 2020 GMC 1500 AT4