Has anyone had any issues with a leaking 3rd brake light? I'm at the dealership now and showed the service adviser a water stain on the headliner close to the rear passenger side corner...It's a spot I've noticed before. It's not currently wet and it rained all day yesterday, so I don't think it's an active leak. But they immediately said that it's potentially an issue with the 3rd brake light leaking. I had suspected it was the panoramic sunroof, but they indicated that it likely isn't as the drains for the sunroof are actually in the front...And that it's likely the 3rd brake light. I have the ESP plan, but they're also saying that this issue likely wouldn't be covered under the plan...which is frustrating (although he did say that he'd work with me on it).

I've been searching for threads on this topic, but not having much luck. Let me know if you've had any experience with this issue.

Thanks in advance.

- Dave

 

Good possibility. Every Ford truck I've ever owned has had the leaking 3rd brake light, except my current one... where's some wood to knock on...

 

While common on older trucks, I didn't think the new trucks had that issue as they changed the way the gasket sits in the housing.Maybe, maybe not?

But, What is common on our trucks, is the rear "pressure release vent" isn't seated right, and causes leaks in the rear cab.

Not saying your 3rd brake isn't leaking, but I have not seen 1 post on this forum about it and I bought my truck new in 2015.
I have seen MANY posts regarding the rear pressure vent (when you close the doors really fast, the pressure difference needs to be released) and then this vent is sometimes not seated correctly and allows water to come in. This is a "common" (but not really) problem with our trucks.

 

I have a 2015 and i had the same leak . The gasket was crimped from the factory and Ford replaced the whole light assembly with no problem .

 

I posted quite some time ago in this thread regarding leaks in my used 2014 F150. I sorted out all of mine, it was a lot of work. The third brake light leaked, The headliner was wet and stained, and the back seats were wet. I replaced the light with an LED while I had the lens off, then installed the lens using silicone sealant on the same gasket. Worked great until I went to a powerful car wash that forced water thru it again. I siliconed the outer edge of the lens with black silicone, problem fixed, but I don't visit that car wash anymore. The water pressure was so powerful I thought it was going to strip the paint off.

My other leaks were from the 2 back pressure vents on the bottom of the back cab wall, water was leaking around one of them into the cab floor and soaking the carpet. I popped those out from inside the back wall of the cab and they fell on the ground under the truck. I replaced the flaps on those things with light waterproof material and sealed the edges of those damn things with silicone and popped them back into their slots. No more leaks there.

The last leak was most of the work, the leak from the sun roof. Actually the sun roof itself did not leak more than it's supposed too, they all do, using drain tubes it's supposed to take care of the problem. I didn't know what was going on with the leaks and the very wet headliner at the rear so I removed the headliner. What a hassle to remove that thing without bending it up and destroying it.
There are drainage tubes on my sunroof, both leading to the front, down the pillars on both sides and tubes going to back and down the space between the back wall where the seat is and the outside cab wall where the window is installed. The front tubes were not the source of the leaks because all the wetness was at the back headliner and on the seats and carpet., The front drain tubes were a bit backed up with dirt. Using a small round brush on a wire I cleared those tubes and also used compressed air to clear them out completely. You can test that they are clear by pouring water down the front drain tubes when the sunroof is open, you'll see them there when the sunroof is open. This would be good regular maintance to check these drain tubes.
The drain tubes going to the back of the truck end up draining the water into the cab space between the back seat wall and the outside wall. There is no drainage holes in this cab cavity for the water to exit the truck, it just sits there and causes rust. If your back brake light and pressure vents in the wall are leaking that water just sits there as well. Now I know why earlier F150 rust terribly at the rear cab corners. What the hell was Ford thinking on this design. I drilled tube exit holes out the back wall so the water could exit the truck and routed the tubes out the holes. I was able to clear those tubes the same as the front tubes and tested the drainage by pouring water toward the back tube from the sunroof. I could see all the water draining on the ground now. I left the headliner out of the truck for weeks, waiting for a number of rain tests.

I now have no leaks, and never go to automated car washes now. I either clean by hand in the driveway or those self wash bays at the car wash. Hope this helps someone.

 

'16 XLT here, yes, my brake light / cargo light was leaking. Sealed it with "Big Stretch" rubber caulking/sealant after very removing and thorough cleaning.
The local body shop quote, "They all do that", even his own truck.
I never use any high pressure hoses or pressure washer.

 

I just had to replace mine! It was leaking bad. Gasket was dried and looks to have failed some time ago. I've only owned the truck since last May and this last month was the most rain I've seen in a while. The truck sits on a stopped driveway so the water runs right back onto the light. The water got in sooooo bad that it soaked the rear of the headliner. Looks like it's been leaking bad for a while, the sockets looked all shorted and burned, which explains why one side of white light didn't work. Thanks to this forum I had the knowledge base to pull from to learn how to pull down the headliner with ease and all of the rear interior panels. I checked everything for additional leaks and found nothing. I found a smoked lense LED replacement light on Amazon that I liked and liked the looks of the gasket. Fairly pleased with the look and it's nice and bright. It's been through a few decent rains since installed and so far all is well. Now that I'm satisfied is not leaking anymore, I finally put it all back together this weekend.

 

It is not common like the previous couple of body styles, but occasionally I see a 3rd brake light on these trucks. Not much, though.