I am having a serious problem with leaking rain into my truck.
I have traced the water accumulating to under the sill plates of the front doors, and if there is enough water it moves to the back doors under the sills too.

Does anyone have an idea of how to find this leak. I have tried looking up in the search feature, but I am thinking either 1) I am not finding anything that applies or 2) I am not searching this too broad. (most of mine are coming back with leaks about parts, not the water leaking in)

Does anyone have any idea what to do or where to look. I do great with pictures if there are any available to guide me.
I really hope you can help, currently I am mopping up huge amounts of water in the river under my sill plates with big huge towels and they are getting ruined and also I am getting that smell in my truck
Thanks

 

Start by watching these 3 videos, they are the most common causes for leaking

How to fix the leak from the marker lights:











How to fix the leak from underneath the cowl:










How to fix the leak from the weather stripping:

 

 

Make sure to get the star screws on the rail too. Run the hose on the roof. If you pull a star screw out and its threads are wet (or rusted), silicone that as well after cleaning the screw and the area.

 

I have had just about every leak you can get in these damn things. I just found a new one, my windshield is leaking in two places now. Go through this list and check them all.

Roof lights, both the corner and the smaller ones in the middle. Easy fix, just silicone around the smaller lights, and silicone the grommet under neath the roof markers.

Check the weather stripping on the doors, the one that runs down the whole side of the truck and down the pillar. They tend to shrink over time and leak mainly in that front corner where it curves down the pillar. I bought a new one for the drivers side, still leaked. I used silicone on that turn and that did the job.

check the cover that hides the blower motor. Its under the cowl by the windshield. Google it, you will find a video. I used flex all tape around that cover, hasnt leaked since. That one was soaking my passenger floor board

check the sunroof drains. one of mine recently popped of, which let the water run into my headliner. That drain line was also clogged.

i put a little silicone on the hex screws that hold down the roof rack rails. I pulled one out once and forgot to put it back in. You would be surprised on how much water can leak in a small hole. Those screws have a rubber grommet that helps seal them that can degrade over time.

Now its my windshield........hopefully after that im good.

The leaks have been the #1 PITA on this truck. It gets frustrating for sure, but they are all pretty simple fixes.

 

lol yeah I just found a missing rail screw on mine by the rear passenger side had to shift an original one under the corner light over to the rail then used a normal 10mm fender screw under the light since there is room there for a normal bolt.

 

Did you get your leak fixed? I am not a mechanic but I have had the roof of my Hummer taken apart and put back and it does not leak now. After you have eliminated all the usual places like front window, roof marker lights, sunroof (mine does not have sunroof) etc. Try checking the groove on each side where the side panel meets the roof panel, there is a black plastic piece that covers it, somewhat like and expansion joint cover in construction if you are familiar with that? This is where mine was leaking. Now I know this is gonna sound crazy but it works and it looks fine, you can’t see it. Wash and clean down in the groove as good as you can (I used alcohol a toothbrush and a clean rag) and let it dry. Buy you a small can of Clear Flex Seal and slowly pour it down in the groove, it works best on a hot day. I filled it just over the top of the black plastic cover from front to back. I did mine three years ago and have not had a leak yet. I even got my headliner recovered afterwards. Shoot me a message if you think this might be your problem, I think I have some pictures somewhere.

 

I had the same issue the waters coming in from the three lights in the middle of the roof just above the windshield check to make sure they’re tight or replaced the gasket

 

Hey all, I have had the same issues. So I started pulling the interior apart to try to find the leak, and decided that while it is apart I was tired of mopping up the water that collects under the door sills. So I covered the cab with a tarp.... it was doubled over and fasten down tightly with bungee straps. (see picture)



It looked like it would be really difficult for any water to find its way into the truck after this....
Well after a good southern rain storm.... I come out to check if we had success.....
NOPE!
The tarp didnt keep the water out.
So I am wondering if anyone has any ideas where this water is coming from...
Thanks for any help

 

The roof is fairly flat and its is not sitting on a hill so the tarp is not going to help unless it is big enough to cover the entire roof as water will just run forward as well as back from the entire back half of the roof that is not covered. Many get some from the outer seal above the doors which continues from above the rear doors to the front and then down.