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Shark Fin Antenna swap, observstions and why they leak

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Ok so I want to put a post together about the onstar, XM, sharkfin, and whatever else antenna we have on the K2xx platform.  I know there have been water leaks plaguing all years from 14-18.  All the posts here I have seen, don’t really have any info or “the dealer fixed it”. 


A lot of people have commented that there is a break in the seal in the rear of the antenna.  Please understand that is not a water seal for water intrusion into the cabin.  That is only a rubber trim from the plastics of the antenna to the metal roof skin. There is a foam seal that goes around the wires and the mount that does all of the sealing of the elements.  When the foam seal deteriorates is when the water issues start.  I will explain with pics a little further down in the post.


So I have a 14 Denali, vehicle was Daily driven, until 2 months ago, has 90,xxx miles on it, sat out side during the day, and garage kept at night.  I have never had any water issues from the antenna (or the 3rd brake light for that matter) 


Here you can see the square seal around the home in the roof was still sealing with no issues 





One of the reasons this post happened was because I found a color matched shark fin brand new for VERY cheap.  And my Denali has the black plastic fin from the factory.  







Edited by 2003 SSEi
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You can see the new seal on the new antenna22A6FA13-2622-4C09-AD2B-F0AD56A16F27.thumb.jpeg.c22f9875993e8133072282e99a209819.jpeg
New crush washer that came with the antenna that is required for a tight seal 
you can easily tell new vs old
The leak fix is to put a bead of clear silicone around the outside of the foam seal before you install it.

Sent from my SM-G965U using Tapatalk

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I understand the fix for the leak.  There is a lot of misconception about how and why the leak occurs.  I guess I was lucky, my truck is 4 years old, 90K and never leaked a drop, while others here have trucks 4 months old and leak.  If the foam seal is compromised your gonna have a leak.  This at least gives people an idea of how the antenna was designed to function

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  • 1 month later...
22 minutes ago, duquephart said:


Saves on wire?

Very viable guess...I’ve read where some manufacturers will remove two threads off a screw or bolt to save weight and cost. When you consider how many screws and bolts are used that adds up. I would suspect you’re correct ?

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On 12/17/2018 at 8:24 PM, 2003 SSEi said:

Differences in antenna size

I believe. That the 15+ antenna and the bigger size is extra plug is for the WiFi 

The bigger antenna with the yellow plug is for trucks with XM  radio 

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4 hours ago, SS502 said:

Very viable guess...I’ve read where some manufacturers will remove two threads off a screw or bolt to save weight and cost. When you consider how many screws and bolts are used that adds up. I would suspect you’re correct ?

I think if that was the case, the antenna would be on the right front corner of the roof, since the wires run to the right side and go to a junction on the right side of the dash.  

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