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Leaking 3rd brake light

26K views 13 replies 9 participants last post by  Spectreniner  
#1 ·
I bought my 2012 silverado extended cab in July.

We had some really hard rain yesterday and today I noticed a little water in the cab on the sides of the floor near the door sills. I have read that the 3rd brake light can leak and sure enough there is water running down the inside of my rear window near the 3rd brake light.

So here are my questions:

-Do they only leak when they are cracked? Where do they crack? I can't see any cracks with it still installed.
-If its not cracked, could just the seal be bad? Replace the seal or just try some silicone, or both?
-Does anyone know the GM part number for the 3rd brake light for a 2012 silverado ext cab? is 25890530 correct?
-If you buy the GM replacement light, does it come with the gasket? If not, what is the gasket part number?

I'm glad this is where the water is leaking and not somewhere more difficult to diagnose or access...

Thanks in advance for your help.
 
#5 ·
I guess this may have been leaking for a while. The floor underneath the vinyl is completely soaked in the entire cab. I guess I need to remove the seats and pull the vinyl up and get everything dried out once I fix the source of the leak.

I'm starting to think it's the rear window seal directly underneath the third brake light, because water is running down the rear window there. But maybe it's the brake light. I'll seal the brake light with silicone as a first measure.
 
#6 ·
No cracks. I found that the gasket collapsed in my case. Not that there is much of one to begin with. I added EPDM "D" shaped weather strips and can still remove the light for bulb changes rather than seal with just silicone that will require more work to replace a bulb. Been working great. !st pic shows proper gasket thickness and 2nd shows top that collapsed and allowed leak. The strips are self stick, but I used silicone to aid in holding things in place better.
 

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#8 ·
Pics are from Feb. 2017 so about 2.5 years old. I would have gone to Dealer under warranty, only they would shove the same junk gasket back in there.
 
#9 ·
I hear that, that isn't very old.
I did a lot of considering when I installed my cab lights...sealing up the cab is not something you want to half @ss.

Sent from my SM-G930V using Tapatalk
 
#10 ·
Pulled the seats and floor out today. Lots of water. Also found a bunch of broken glass. Rear window was replaced at some point and not sealed properly. As soon as I put a little water near the top of the rear window seal (not getting any on the third brake light at all) water poured right in. So I need to get the rear window re-sealed or replaced. I will seal up the third brake light also to help prevent another flood later on.
 
#11 ·
I have the same problem, the light's gasket is not adequate. The dealership changed out the light and got the surface water vacuumed. I spent all day today (Friday) sticking towels under the sill plate and had a fan blowing on the carpet. Dealer said it would dry out on its own. They were very nice to get the lamp changed quickly and remove some of the water but I am concerned about the water that may be trapped under the carpet. The headliner looks good, maybe just a little discolored so I think that is OK but hate to leave water standing under carpet because it may mildew.
Should I take it back and ask (again) to remove the carpet and make sure it is dry?

Regards,
Ed
 
#13 ·
I've been having issue with water in my chevy. It was leaking thru the 3rd brakelight and I siliconed it in with LED lamps. I was still getting water in truck. So we pulled backseat and took headliner down and put water on it and no leak. Then we noticed water on the floor. Pull back the sound proofing and there are two cab pressure vents on each side and water was pouring in thru them. The rubber seals were rotted and cracked allowing water to come right in everytime it rained. They have rubber flaps that were rotten also. I was going to silicone them in , but decide to buy new. I still may silicone in the new ones. I bought new vents at getoemparts.com