Water intrusion

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Cougar281

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Sep 11, 2006
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I've been having water get in on the drivers side, soaking the carpet, but I haven't been able to find anything to point to a general location that the water is getting in, until today. I found it running down the side of the parking brake and dripping from there.

Does anyone have any thoughts as to where it could be entering, before I unnecessarily tare apart half the truck?

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2004LB7

2004LB7

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Can you cause it to leak with a garden hose around the exterior? I'm thinking either windshield sealant or cowl
 
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Cougar281

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Sep 11, 2006
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Haven't tried it.... Going to have to wait for the weather to dry out to try. Is factory windshield sealant letting go or leaking eventually a common issue? My Cougar has had a leak in the back for years that would cause the trunk to fill up with water (It lives inside now), and I suspected the rear window, but an auto glass guy told me that typically, undisturbed factory sealant doesn't 'just fail'.
 
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Cougar281

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So I just went out to take another look, and I noticed a drop hanging off the bottom of my guage pillar...


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I also noticed for the first time that the corner of the headliner at the A pillar is damp, suggesting the marker light and/or onstar antenna as possible culprits...
 
2004LB7

2004LB7

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That would be my next guess. Either the antenna or roof marker lights. My Jetta had a leak at the antenna. A loosened it up, put some polyurethane sealant under it and tightened it back up and hasn't leaked since. Going through the headliner was a pain
 
DuramaxRamRod

DuramaxRamRod

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My dad's '03 had rust on the cab and was pushing out the windshield but it was pretty obvious with water coming down the inside of the windshield.
 
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Ron Nielson

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Oct 11, 2009
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My method is to use painters tape and cover as much of the suspected area as you think might stop the leak. Then apply water and see if the leak stops. If still leaking, increase the coverage area; if the leak stops, remove some of the tape, say 25%, and see if it begins again. If it leaks, find the leak precisely in that 25% removed area. If it doesn't leak with 25% removed, remove more tape and test again.
 
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Cougar281

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Sep 11, 2006
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Ugh. Found I have leaks everywhere lol. Pulled a bungee cord out from under the flap behind the rear seat and it was wet. Found the cab vent seals are cracked and leaking.

Edit: will the newer GMT900 LED cab lights fit on a GMT800, or is the roof profile too different?
 
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1FastBrick

1FastBrick

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Cougar281 said:
Ugh. Found I have leaks everywhere lol. Pulled a bungee cord out from under the flap behind the rear seat and it was wet. Found the cab vent seals are cracked and leaking.

Edit: will the newer GMT900 LED cab lights fit on a GMT800, or is the roof profile too different?
Click to expand...
Seen a few people do it . maybe put silicone underneath to seal it?
 
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Cougar281

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1FastBrick said:
Seen a few people do it . maybe put silicone underneath to seal it?
Click to expand...
That was pretty much why I was asking... It seems putting silicone under leaking clearance lights resolves the leaking, but it would also make removing them 'more fun' when a bulb goes out, so if I could replace them with newer LED units and silicone them, it's 'less likely' I'd have to remove/replace one down the road.
 
PureHybrid

PureHybrid

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Feb 15, 2012
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If you look at how the cab is molded together at the roof, water can come in at the 3rd brake light and take multiple different paths depending on how the truck is sitting. That would be my first guess
 
Nate’s Dmax

Nate’s Dmax

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Dec 11, 2020
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Yes if the truck came from factory with the cab lights the newer style will not work very well. I would get a new LED set for the model year and caulk them a little on install.
 
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