100% SOLVED. We had extended rain this week that would have certainly leaked before the silicone I used to cover the crack line. Really helped talking it out through here, the windshield quizzing sent me to the glass shop, and there's where a good set of eyes found the issue. Thanks everyone.
99% SURE I HAVE FOUND THE PROBLEM: This is a bit embarrassing, but it's amazing what a new set of eyes can see; I stopped by a Safelite shop (Alton IL, praise to the tech who helped me). He took a look at the windshield seal and of course, not finding anything with the seal, he saw a hairline crack in the center cab light. I completely missed this, never saw it while doing all my seal work; if you push on either side of the crack there's a reveal big enough for water to get thru. For a test repair, I've done another short-term silicone bead worked into that crack & another over it to see if the heavy rains we have predicted tonight/tomorrow put it to the test. I'm sure this is it - likely changing out the whole fixture as soon as we get some decent working weather. If this is the final source of water leak, then I"m just left with whatever damage it did to the compass/GPS/XM module. Thanks to all of you for points & feedback.
Great feedback - I was sensitive to the question of over-tightening, I could see how soft the metal is around the hole when I had it out, I feel pretty good about the tension & put into it, but the locktite is a good put that I didn't do & will on my next change of the antenna if I still need another one--through all of this, still have no compass/GPS. I think I got to the bottom of my problem yesterday, post below.
This is the kind of validation I was looking for ... in all the vehicles I've owned in my life, never had a windshield leak, so I figured this was a remote possibility, and it probably is very rare, but given all the responses above, I'm going by a glass or body shop for a check and see what they can do/find. Thanks for the post.
Hah, yeah, I was joking about using Flexseal anywhere on my truck. Hindsight, certainly should have taken it to the dealer right after the incident in late 2018, at least it was only out of warranty on miles and I might have had half a chance of getting some credit. I am going to get to the bottom of this, appreciate your points, thank you.
Yep, agree, I've been 1) hoping to not have to go that far after watching a long video of a headliner change-out removing seats & all--I'd hope not to have to go thru that much just to drop it, and 2) warmer weather, I have nothing more than a driveway. My only water test may still have been fooled because I only had it sheet from rear-to-front and didn't do a 'peek' by dropping the passenger side corner. Great point, I appreciate the reply, thank you.
Nothing distinctive that I can tell; there's always general wind noise to my constantly ringing ears. There's a rubber-type flap seal along the top-to-roof joint that hides whatever 'wedged' seal is actually between the windshield and the groove in the roof. I don't know much about how a windshield is mounted, so I'm thinking it's time to go to a windshield shop or a body shop, have the seal checked out by somebody who knows what to look for. Thanks for the response.
Don't know for sure, I bought it used; had one tech read through the dealer history but he wouldn't/couldn't print it for me, and didn't mention anything out of the ordinary other than services & oil changes by the original owner. Doesn't mean owner didn't have a rock-strike & changed it out somewhere else. Are you thinking maybe a botched replacement? didn't leak or lose the antenna feed until months after I had it, can a windshield seal 'go bad' over time?
PapaBear7 started following New Member / Roof Leak - maddening Water intrusion
Thanks for that FlexSeal ad - if they make it in brown, I may be going there next. After I did the silicone job on all the fixtures on the roof, I dropped the corner of the headliner over the driver seat, same corner I pulled down to work on the antenna twice ... ran a hose over the roof for a half hour, letting it sheet over everything on top, and didn't see any leaks. Now we've had 2 months of cold since all that, so I stand to go on top & check that the silicone beads haven't shrunk, but it was a good, clean application getting first pass under the edges of lights & 2nd pass clean bead on the outside of all fixtures. I'm suspecting the top line of the windshield.
Hello everyone, just signed up and hope to find great help here ... I've used other forums for other vehicles, and always find great points & help from fellow members, and hope to return the favor as well. I bought a 2016 Silverado / Duramax LTZ two years ago, just out of bumper-to-bumper warranty at 40K miles, still going strong on the 5-yr engine warranty. My problem is a persistent roof leak, driving me crazy. First world problem, but absolutely should not be happening on this truck. I've chased shark-fin possible source, and have no indications that it's the other common leak area, the rear mount center light. Much research led me to the XM antenna; I was sure this is the problem, because I've lost GPS/XM/wifi when I started noticing a leak showing up at the front & sides of the overhead console, wet headliner. This was Sep, 6 months after I bought it in March '18, so I didn't even try to go back to my dealer & complain, figured they'd respond like I've seen others report "oh no, on you to fix". I just lived w/ no GPS, use my phone anyway. I waited all the way to Aug 2019 (had very few leaks thru summer 2019) to buy the updated design shark-fin model & replaced it myself, first trusting the rubber seal & new design. This did not fix the XM feed, so I finally got in touch w/ GM Customer Service, and after two trips into a different (local GMC) dealer, they only did minimal diagnostics on the electronics side, didn't do anything else with the antenna mounting or leak check. So I gave up again, pulled the shark-fin off & used a good automotive sealer to supplement the new-design antenna; remounted it. Still no electronics, but now hoping the water stops ... but no, rain storms still wet the headliner. My last effort has been to use the same sealant around all of my cab-lights, and at the seals of the rear-center high-mount light. Just moved my truck after a day of light drizzle here, it was dry at first touch, but after reshuffling in the driveway, drips from the low-point sides of the overhead console, at the front. No water stains at the back window. Maddening - I did a very solid sealing job around all the penetrations in the roof, cab-lights, rear-light, & antenna. And still water. Has anyone else dealt with anything close to this? or have any insights? Could there be a leak along the top of the windshield? It doesn't apppear that could dribbling into the console area of the headliner, but who knows? Appreciate any pointers - I have always been a GMC guy, put same faith in this truck, but this is such a maddening issue I'm just at wits' end. Obviously, I could take it in and pay god knows what for hours of diagnostic/fix out of warranty, but just eats me up that this just should not be happening at all.
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