Bought a 2017 Denali from a used lot in October 21, truck had been traded in and imported from another province, body is in great condition compared to others it’s age in Ontario Canada! Deal! About a week into driving it I noticed the carpet was wet front and back driver side... no major signs of where water was getting in. After the 3rd brake light was replaced and shark fin sealed by the dealer I got the truck back home and carpets were soaked the next rain. Drove the truck this way for a couple months in the winter. No call back from the dealer when I decide to reach out again.
After some digging online I pulled the back seat and checked the cab vents by spraying with a hose from outside. Rivers of water coming in and flowing to the low spots of the floor.
I pulled the cab vents and sealed up the rubber seals with clear silicone and stuck the vents back in (cure overnight in heated shop while secured with a bungee),dried carpets with fans overnight after vacuuming most of the water out. sprayed underside with Lysol to kill any mildew. No more leak with garden hose or high pressure car wash.
Dry Carpets for the first time since I’ve had the truck!
Hope this helps anyone else having water issues in the cab, I had some trouble finding info online.
Here are some photos from the job