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PapaBear7

New Member / Roof Leak - maddening Water intrusion

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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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Seriously though. I wonder how much work it is to remove the headliner . Get a few people in the truck and go to the car wash. Everyone should have a flashlight and if there's a leak somebody will see it. No? Sounds good on paper.

Anyone else got anything?

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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.

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Is it a factory windshield still?

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13 hours ago, Lsgun1 said:

Is it a factory windshield still?

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?

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Do you hear any wind noise from the windshield? That's a good indicator of a bad seal. My work does windshields and we get quite a few returns with bad urethane seals.

Sent from my SM-N975U using Tapatalk

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11 hours ago, PapaBear7 said:

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?

Anything is possible. Your best bet is going to be to remove the headliner completely and use a hose to isolate where the water is coming in. Start on one of the roof mounted items at a time so you can pinpoint versus soaking the whole roof and guessing. Water takes the path of least resistance so it doesn't always flow the way you think.

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On 2/17/2020 at 8:55 PM, PapaBear7 said:

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.

After seeing dieselfan1's post  I looked up Flex Seal and can think of a few potential uses around the house!   I wouldn't use it on the roof of my truck nor would I get generous with silicone seal. It is most unfortunate that this wasn't dealt with while under warranty but the experience has paid dividends in the, "What I'd do next time" department.    We all know water intrusion in your RV, house, or vehicle will have long term major impact if not stopped early.  I think you've done a commendable job at addressing this problem but now its time for the professionals, imo.  If it came to this point for me, I'd drive to a reputable body shop or two and get an estimate to get your truck back to original condition.  I'd think this would involve; take out the headliner, re and re all potential intrusion points (including windshield if necessary)  test and then provide a guarantee!   Your '16 LTZ DMax holds considerable value and is worth this level of investment.

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Not on the same generation truck but I had a similar problem on 07 Yukon I owned. I was having the same issue in the same general area. The windshield adhesive had came loose. You said you weren’t sure if it was the original glass or not. Might be worth the $1-200 to reseal the windshield at this point.


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14 hours ago, durandetto said:

Do you hear any wind noise from the windshield? That's a good indicator of a bad seal. My work does windshields and we get quite a few returns with bad urethane seals.

Sent from my SM-N975U using Tapatalk
 

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.

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14 hours ago, Lsgun1 said:

Anything is possible. Your best bet is going to be to remove the headliner completely and use a hose to isolate where the water is coming in. Start on one of the roof mounted items at a time so you can pinpoint versus soaking the whole roof and guessing. Water takes the path of least resistance so it doesn't always flow the way you think.

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.

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12 hours ago, Donstar said:

After seeing dieselfan1's post  I looked up Flex Seal and can think of a few potential uses around the house!   I wouldn't use it on the roof of my truck nor would I get generous with silicone seal. It is most unfortunate that this wasn't dealt with while under warranty but the experience has paid dividends in the, "What I'd do next time" department.    We all know water intrusion in your RV, house, or vehicle will have long term major impact if not stopped early.  I think you've done a commendable job at addressing this problem but now its time for the professionals, imo.  If it came to this point for me, I'd drive to a reputable body shop or two and get an estimate to get your truck back to original condition.  I'd think this would involve; take out the headliner, re and re all potential intrusion points (including windshield if necessary)  test and then provide a guarantee!   Your '16 LTZ DMax holds considerable value and is worth this level of investment.

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.

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6 hours ago, da90 said:

Not on the same generation truck but I had a similar problem on 07 Yukon I owned. I was having the same issue in the same general area. The windshield adhesive had came loose. You said you weren’t sure if it was the original glass or not. Might be worth the $1-200 to reseal the windshield at this point.


Sent from my iPhone using Tapatalk Pro

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.

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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.

The mobile glass company said mine had been replaced and during that process they didn’t prep the glass correctly causing it separate. They also told me to expect to replace the glass because they couldn’t guarantee removal without damaging the glass. We were able to reuse the glass thankfully!
369797272277d3893ff4de99a48c86ef.jpg


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