Codeman317

I have a 2010 F-150 XLT that has the standard leak in the back of the truck making the liner both corners near the passenger doors soaked and stained. A couple of years ago, I had an auto glass company reseal the window and I also put a bead of silicone on top of the third brake light. I have the truck cap on my truck, so it's very difficult to silicone on the bottom of the light, but overall, it seemed to fix the leak. Fast forward to this week up to yesterday - lots more water in the back of the truck in the same areas. Because the glass guys said that they used the toughest caulking to seal the window, I have a feeling it's not the window and so did the window repair guy I called out yesterday. I thought that it could be the tail light again so I heavily resealed the third brake light. The two rubber seals with the rivets on the roof on each corner of the truck seemed like they were getting dry rotted so I also heavily siliconed those as well, but again, since the truck cap is on, I basically only covered the top of those seals, and not the part that connects to the window. I tried to dry the inside of the roof after that and then came to check it this morning. Water is still getting in!!

Do I need to move the truck cap to get the third break light off to reseal it from the inside? How is the water getting past the silicone? I have so many questions about why this is happening again, but unless I choose to pay Ford $150 just to agree to look at my truck, I have very few answers.... Does anyone have any insight as to what to do/what is causing this after sealing the truck already?

Thanks!
Cody

Chad Walker

One thing - silicone is not ideal as it traps moisture which causes more problems down the line, I am not sure what "toughest" caulking means but if they were using 3M Windoweld then maybe that is what they mean since it does come in a caulking tube. A butyl seal is all it needs though and seems to stay more plyable. I would drop the rear of the headliner and have someone spray water on the back window and the 3rd brake light. I am betting on rear window though.

Spiky

Isn't "traps moisture" what you are looking for? This isn't completely enclosing something, just sealing edges.

white08gt

check the seam sealer on the roof

5.0nly

Chad Walker

Traps moisture under the silicone promoting rust among other things, so no this is not what you want as a fix.

Spiky

Ok, but we're talking about a line of product around an edge of something, 3rd brake light for instance. What product would behave differently? I mean, silicone based caulk is the standard for tubs and showers to block moisture from going underneath the seal. Nobody claims it makes the moisture problem worse there, in a far more wet area. RTV is silicone based for sealing and gaskets. Lots of products are.

TimelessR1

I recommend TAPING all the way around the 3rd brake light...yes TAPE! and leave the tape on untill after a rain storm. this will tell you IF it is the 3rd brake light. I used 3M masking tape when i checked m ine this way when i pulled the tape off there wasnt reside to try and clean off.

If the tape does stop any leaks, THEN yes remove the entire brake light, use an RTV , or comparable sealant and use generously around the 3rd brake light, use enough that it squeezes out around the edges when reinstalled. maybe even dab a little on the screw threads to create a seal there also.

If it still leaks during the taping process, leave it taped and move to the next culprit ( the rivots) and so forth. I even taped the entire window at one point checking if the window seal was the leak......

turned out IT was the 3rd brake light...9 times out of 10 its the light!

good luck!