2016 2500HD Denali roof leak

Mike Hamm · March 31, 2017

Mine started today. Looks exactly like yours.

Ugh. Don't be surprised if the bottom of the knee bolster on the driver's side dash is wet and there is a line of water right under the dash on the floorboard.If your TPMS and keyless entry stop working, those both go to the RCDLR that is in the dash and can get wet from this leak.

Peterd · March 31, 2017

Mine started today. Looks exactly like yours.

Picked up new truck Wednesday. Usually garage it but since it has been raining for the past two days it is outside Hope it passes the water test

My. 2015 had the leak so odds are ?????

Peterd · March 31, 2017

Picked up new truck Wednesday. Usually garage it but since it has been raining for the past two days it is outside Hope it passes the water test

My. 2015 had the leak so odds are ?????

.

Guess if it stops raining I will have to change photo

cford716 · March 31, 2017

Ugh. Don't be surprised if the bottom of the knee bolster on the driver's side dash is wet and there is a line of water right under the dash on the floorboard.If your TPMS and keyless entry stop working, those both go to the RCDLR that is in the dash and can get wet from this leak.

That's where I first noticed it, a pool on the floor mat under the parking brake pedal.

Stopped at the dealership today. They were all to aware of the issue. Asked if I wanted them to do it right then. He said they had done so many they can have it done in 30 minutes. Unfortunately didn't have the part, but overnighting it so they will do it tomorrow.

I asked him what is different with the new part. He said the seal on these was small and wore quickly. Said the seal on the new antenna is larger. I would suggest if you have a 2016 you get it changed. Sounds like it is more likely a when than if it occurs. So far he said 2017's have not had this problem with the new part.

Edited March 31, 2017 by cford716

3Money · April 6, 2017

Mine started today. 2017 Sierra Denali 1500. Guy at dealer acted like he had never heard of such a thing. LOL. Sitting at the dealer now. We will see what they say.

rws262 · April 6, 2017

Ugh. Don't be surprised if the bottom of the knee bolster on the driver's side dash is wet and there is a line of water right under the dash on the floorboard.If your TPMS and keyless entry stop working, those both go to the RCDLR that is in the dash and can get wet from this leak.

Does the water on the floor come from the same leak from the antenna fin? For the record, I've got the leak too. Bought new in August 2016, currently has 14k miles.

Mike Hamm · April 6, 2017

Does the water on the floor come from the same leak from the antenna fin? For the record, I've got the leak too. Bought new in August 2016, currently has 14k miles.

Yeah, same leak.

rws262 · April 6, 2017

Am I better off fixing it myself with Silicone or taking this into dealer? Just noticed the leak started with the recent rainy weather.

cford716 · April 6, 2017

Does the water on the floor come from the same leak from the antenna fin? For the record, I've got the leak too. Bought new in August 2016, currently has 14k miles.

Yes. I first noticed a small puddle under the parking brake. It was dripping from under the dash onto the parking brake pedal and the floor. Later it was wet on the left windshield post and at the pivot point for the drivers visor.

Dealer was very aware of the issue and said they have done a lot of them. If your dealer is telling you otherwise its either a lie or they don't sell many trucks. Quick easy fix. Apparently a redesigned seal from what the collision shop said.

Edited April 6, 2017 by cford716

cford716 · April 6, 2017

Does the water on the floor come from the same leak from the antenna fin? For the record, I've got the leak too. Bought new in August 2016, currently has 14k miles.

Duplicate post

Edited April 6, 2017 by cford716

cford716 · April 6, 2017

Am I better off fixing it myself with Silicone or taking this into dealer? Just noticed the leak started with the recent rainy weather.

Its under warranty, get it fixed!

pm26 · April 9, 2017

They all have that gap in the gasket at the back. I don't know why but they do.

There is a reason for that gap. The antenna base has a double seal. The outer seal is just dust seal and the gap is there to allow moisture to escape. The actual water seal is under the center of the base, smaller than the outer seal and it is that inner seal that actually keeps the water out. I suspect that they are not tightening the bolt on the underside of the antenna base to compress the water gasket sufficiently, or the bolt comes loose. Or the seal is somehow misaligned. Then the seal is no longer watertight and water intrudes inside the truck through the bolt hole.

Maybe they could have come up with a better design. but given what it is, it will not leak if assembled and installed properly. I have a similar antenna base on my 2009 Impala LTZ and it never leaked a drop in 115k miles/8 years.

cford716 · April 10, 2017

There is a reason for that gap. The antenna base has a double seal. The outer seal is just dust seal and the gap is there to allow moisture to escape. The actual water seal is under the center of the base, smaller than the outer seal and it is that inner seal that actually keeps the water out. I suspect that they are not tightening the bolt on the underside of the antenna base to compress the water gasket sufficiently, or the bolt comes loose. Or the seal is somehow misaligned. Then the seal is no longer watertight and water intrudes inside the truck through the bolt hole.

Maybe they could have come up with a better design. but given what it is, it will not leak if assembled and installed properly. I have a similar antenna base on my 2009 Impala LTZ and it never leaked a drop in 115k miles/8 years.

As I posted before, I was told that the replacement antennas, same as on the 2017 model, is a new design of the seal. The dealership said they have replaced numerous ones, the seal was too thin. The new ones have thicker seals.

I didn't see the new parts to compare but that's what I was told.

Sent from my iPhone using Tapatalk

Edited April 10, 2017 by cford716

Mike Hamm · April 10, 2017

There is a reason for that gap. The antenna base has a double seal. The outer seal is just dust seal and the gap is there to allow moisture to escape...

...but given what it is, it will not leak if assembled and installed properly...

But the problem is the gap is on the uphill side of the antenna. There is no gap on the downhill side so moisture can't escape. Water on the uphill side heads downhill right into that gap and doesn't have anywhere to go once in there. And the sharkfin starts filling up with water. Once there is enough water in there, it gets past the inner seal. When I discovered the leak and thought it might be the sharkfin, I wiggled the sharkfin and a ton of water came flowing out of it. It was full of water. So, the gap IS a problem on these trucks because it lets water in but won't let water out.

And, the "assembled and installed properly" is a huge red flag. Proper design and assembly procedures that don't require an assembler to properly put it together will prevent this. Take the assembler out of the process and the problem goes away. Any time a person has to make a subjective decision (tight enough, too tight, correct orientation, etc?) there will be problems. Make it so the assembler just has to put it on and not have to make any decisions about how it gets installed. Proper design will make it so that can happen. Proper process development will ensure the assembler can't make a mistake. The old phrase "technician proofing" applies here. It amazes me that this problem has been around since at least 2014 and it hadn't been addressed at the assembly line. Yes, it seems like maybe the 2017 models have addressed it, but now there are a bunch of unhappy 2016 owners who should have the benefit of lessons learned from the previous years. I worked many years as a process engineer and this is a prime example of poor design and assembly process. Time will tell regarding the 2017s.