Prof

We have had a lot of rain here recently, and when taking the truck out yesterday, daughter heard sloshing water. I tore the door sills off, and there is water sloshing around in the channels underneath. So I undid the rubber plugs on both sides and drained the water out.

I already replaced the third light several years ago, so I am wondering if this is a problem with the sliding rear window. Could enough water come in the bottom of this thing to fill up the sills? I am worried about corner rust at this point, I haven't gotten in there to put a light to it, but damn, it was a lot of water.

Any ideas?

lewissa81

I'll start with saying that I hope you have an easier time finding your leak than I did. It took me about a year to find and seal it.

You can search on the forum and Google, and there will be hundreds of stories like this, most without a definitive solution aside from the third brake light. Here's a quick list of what I remember.

If both sills, passenger or driver side have water:
Third brake light
Rear sliding glass
Sunroof drains
Body seam on lower REAR firewall
Door checks
Door wiring harness
Windshield leak
Windshield stop mounts
Clogged cowl drains located at bottom rear of front fenders
Body to door weather stripping
Interior door drains
Any of the harnesses that go through the firewall

Passenger side:
A-piller intrusion behind fuse block

Driver side:
Body seam on far left firewall corner.(this was mine)

With my leak, I couldn't replicate it with a hose until I opened the hood and sprayed a little cubby hole under the brake booster. Even then, I had to be parked at an angle for it to leak. I'm still not sure how or why it would leak when raining, but not with a hose unless I sprayed that one spot, but it quit leaking once I sealed the seam.

Prof

Could the rear slider weatherstripping, if bad, allow that much water in? That weatherstripping is damn expensive to replace, but I will do it if necessary. It seems like, instead of any water in that rear window channel would drain down holes to the ground, as it is foreseeable that RAIN could get in that channel!

All my other seals are pliable and good...and my truck wasn't moving when the rain hit ...so the moisture surely would get down into the firewall with the hood closed?

Thanks for the reply.

Prof

Does anyone know the part number for the rear power window weatherstripping and a cheap place to pick up the kit? I found this once, can't find it now...

Thanks

lewissa81

The sills could have filled up slowly, so keep in mind you could have a small leak.
What I remember of the rear slider, is that the drain channels can get dirty and not drain properly. I have a stationary rear windshield, so I didn't focus on it. I'm sure a specific search will give you more info.
Water can and will run down certain paths to get under the hood. Mine didn't leak while driving, or on flat ground. It only leaked when I parked nose uphill (which is how I park in my driveway).
My advise is to get a hose and start spraying where you think the leak is first. Check all of your carpet and completely dry it, including underneath the carpet.

Nocturnal1

Finding a water leak can be tricky as others mentioned.

Maybe run a bead of silicone between the third brake light and body at the top of the third light, and re-tighten the screws. It may have loosened in the years since you've replaced it. It's a 5 min job and may give you confidence that it isn't the third light. It may even eliminate the leakage!

I had to do that to mine a few months ago.

Mod (Ret.)

To properly seal the third brake light housing, you have to remove it, remove any old silicone (if it was sealed this way once before), then place a bead of new stuff, and let it cure according to the instructions on the tube! Many folks slap a bead on, then instantly bolt it on. This makes the silicone act like industrial strength epoxy glue; it will be difficult to remove the assembly again; some have ruined the paint, or busted the assembly trying to remove it later to change a bulb.

micco

Any Updates Prof on your leak?

I'm in the same boat with my 06 Lariat, water in both sills.
I checked 3rd brake light - looked good.
My sunroof was replaced, so i think i might remove the headliner to ensure they attached the drain plugs...but i'm hoping you can provide some insight on your solution before i start tearing things apart.

Prof

I have pulled the sill plates and been waiting for rain...they were a little damp today. I have been backing up my incline driveway to see if I could get the water to run back to front. I am starting to think the leak isn't from the back window, but coming from the front of the truck somewhere.

I am totally befuddled.

micco

Ya mine is parked on an incline nose up.
With the sill plates off i don't see water entering the rear of the channel. So i'm also assuming it's coming from the front. There is also gravel and dust at the drivers kick plate - almost like there is a hole or something.

I'll post anything i do that yields results...winter's coming (no GoT punn ) so i'd like to have this resolved.