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2015 Canyon
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Discussion Starter · #1 ·
Ran my '15 Canyon through a car wash about an hour ago and noticed water dripping and running down the inside of the window as I was driving home.
Not really at the center. It's a bit more on the passenger side. Not sure if it matters, but I have a Bose radio with Sirius/XM and Nav.

Is this a common issue with the 3rd brake light or should I focus on the antenna?
Also, how difficult is it to remove the back of the headliner to access the bottom of the antenna? ...As you can see, I do not have the sliding rear window on my setup.

If I forget to mention it...
Thank you for any help that is provided!
 

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2021 Black \/6 4WD Z71 Crew Cab Short Box
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Both can leak- the third brake light is a known issue.
might look at the shark fin antenna mod threads as the y detail dropping the headliner. Also while you’re in there you could do that mod as pulling the headliner is the hardest part.
 
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2017 Chevy Colorado Z71 Extended Cab 4WD Summit White
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Well you might need to reseal the High Mount Brake Light.
I can't find the actual part... But Silicone always would do the trick
 

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Well you might need to reseal the High Mount Brake Light.
I can't find the actual part... But Silicone always would do the trick
Very true especially on first generation. With them not so much will third brake light leak but when. When I had my new 2007 Canyon I took the third brake light off and flipped it ( commonly done it looked better with curvature of truck) after sealing it with black silicone. Had truck nine years and it never leaked.
 

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2017 Chevy Colorado Z71 Extended Cab 4WD Summit White
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Very true especially on first generation. With them not so much will third brake light leak but when. When I had my new 2007 Canyon I took the third brake light off and flipped it ( commonly done it looked better with curvature of truck) after sealing it with black silicone. Had truck nine years and it never leaked.
I had a little water on the ibside glas passenger side of mine after changing mine to a LED Center Mount Brake Light. Used some clear silicone and no issues since.... And I get my truck washed at least once a week
 

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2015 Canyon
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Discussion Starter · #6 ·
I would think that I'd see a water leak or soaked area further in from the rear window if it were the antenna seal. Then again, the water could have simply run down to the nearest outlet.

I'll look for a new seal on rockauto or a GM Parts retailer. I would like to upgrade to a sharkfin, but I'd like to trace the leak as a first step.

Many thanks!
 

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2015 Canyon
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Discussion Starter · #9 ·
I ordered this on Amazon yesterday. Says it fits the '15-'20 models:

Had it apart today and I'm 95% sure that it was coming from the 3rd brake light. There's also a bit of water on the inside of the whole 3rd light assembly so I'll be drying it out and using clear caulk along it's inside perimeter once I'm ready to install the gasket. Ordered some new 921 LED bulbs also 👍

I'm not messing with the antenna -as of yet. If I still see a leak once the 3rd light has been properly sealed, then I'll go ahead and order a sharkfin setup and make my own gasket for the bottom of it.
 

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My poor mom had a leak on her drivers side door around 2010 on a different GM car known as the HHR. She took it in many times, it couldn't get fixed. She messaged GM in tears, using the little form on the website. It became lemon.
 

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I received the gasket on Friday and will install it this weekend.
hope you have good luck with it.

I bought that gasket a while back when i was trying to fix my aftermarket third brake light headliner leak. It worked fine until it gets a constant soaking and the gasket material got saturated and let the water leak past again.

Maybe I got a dud but I eventually just sealed it with silicone afterwards.
 

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You'll get the best seal using silicone sealer. I used black silicone sealer on my 2007 Canyon and drove it 9 years and it sat outside year round and never leaked a drop. Being a what if person I took the light off before it was leaking and siliconed it.
 
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2015 Canyon
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Discussion Starter · #15 ·
Ok, so I found where the leak was coming from and it was not a faulty gasket. There's two parts to the 3rd light housing and the area where the Yellow Circle is showing came loose (in that whole corner) and was allowing water to get into the housing. That section is not sealed by the gasket, so I used a clear silicone between the two parts and let dry overnight. I also used the new gasket, but I think I'll just do what many of you have mentioned already and just make my own gasket next time with silicone...if I need to remove it again.
 

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If you use black silicone sealer as I posted above put it on thick and its ok for it to be swishy some when you tighten screws putting light back on. What pushes out is easy to clean off. Just get up in the bed (easier than trying to reach) and wipe off the excess with mineral spirits (it won't hurt your paint). I guarantee you that 3rd. brake light will never ever leak from the gasket not seating tight enough to keep water out.
 

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2016 Colorado WT, crew cab long bed
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I had the same leak. I just ran a bead of clear silicone on the outside of the light against the cab. Too lazy to take my shell off to get in there but so far the silicone is holding up. Unfortunately for me, it stained my headliner a bit before I noticed the leak.
 
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