[Sjo4]

I ended up taking my Terrain to my normal independent shop. He said there were two factory cut holes along the pillars of the rear hatch that had some type of tape (like a thicker duct tape) over them that had deteriorated. He said he put a new patch and seal over the holes. It seems to have stopped the water getting in for my case. Honestly I think you'll have to just take it somewhere and have them run their water test to find the leak. My mechanic had my truck for 2 days hunting down the leak. He had to take interior panels off to find out where the water was leaking from.

 

[Sjo4]

I found those patches to be leaking on my 2013 terrain- easy to fix by removing the tail lights and block back up with duct tape. Would make more sense to put a rubber grommet in the hole though. However, I still have leaking. seems to be coming in the bumper area- I get a small leak when hosing water over just the area by the lower tailgate and can watch it leak in there. Not sure of the fox for that.

 

[EdManning]

I think there is a rubber plug in the spare tire well to run the wires for trailer lights. Remove the plug and no damage to gas tank or lines. It can replaced if you want.

1st photo is the tape from the factory that did not stick, the 2nd and 3rd are after I use RV roof tape and pipe dope to file in the area first

 

[kbz1960]

Weird. Why they even need that there.

 

[EdManning]

Weird. Why they even need that there.

The only thing I could thing of would be if somebody needed to tap into the wires for the lights.

 

[SFCruiser]

Just a followup on the water leak. The dealer replaced the sunroof frame under warranty. It has been four months since the dealer repair and no more water leaks.

13 months after the sunroof frame replacement for the water in the spare tire area, I again have water leaking into the spare tire area. This was on November 16, 2020. The dealer this time replaced the sunroof drain hose. The mechanic left dirty fingerprints and cracked the rear port side panel. The dealer cleaned the area and replaced the panel.

 

[rednox301]

See attached pictures of a 2014 Terrain, holes factory made, it's very obvious how dumb USA auto industry is, I can't believe that any foreign vehicle is way more quality than USA ones, it;s embarrassing. I had to take off the trim by the latch and both sides panels in order to track the incoming water after I opened the water hose aiming to were the tailgate gap is, nothing to do with gaskets or mastic or anything like that, it was just the poor quality of the most vehicle made in USA.

Good shot of your Fuel Pump Power Control Module in your last pic.
It's mounted on the floor in the spare tire storage area.
Definitely want to keep that dry.

 

[Humbertonavarro]

Have not drilled a hold in spare tire well to allow water to drain. Over the years, I have experienced water leaks on several vehicles (but not a Terrain).

You do run the risk of damaging a fuel tank, fuel line, evaporate line, wiring harness, etc. Exhaust fumes could enter the hole, such as while you’re stopped with the engine running. If you don’t stop the source of the water, you run the risk of mold and mildew, and respiratory issues.

Hello I have a terrain 2018 and it present exactly the same problem.

The problem its realy simple to resolve Just look the end of the drain tube under the rear fence try the other side whit water to view the water runing out.

After locate the correct drain just introduce on it some kind of wire guide until the water start to drain ant thats it.

 

[msera1]

So great to discover this thread and seal the tail light body hole with some Gorilla Waterproof rubberized tape. Of course i had water in the spare tire well but see i have a wet rear seating rug. Does anyone have experience that this is also caused by the tail light but have a hard time believing the water traveled there. SO then what is the cause of the next leak, from the roof seam or rear sunroof drain? thanks for any support you may have.

 

[msera1]

I also had this issue and it turned out to be the taillight assembly. I didn’t know the water was coming from the tailgate. I thought it was coming from the AC drains or windshield because that’s where the water was traveling to the front carpet area since I park on a slight hill. This caused havoc and the water started evaporating and condensation started to cause electronic problems. The dealer wanted to charge $5k+ just to fix the problem but I was able to get it fix cheaper (thank GOD) and I just used sealer to stop the leaks in the tailgate area.

you think the rear tail light leak was also traveling to front?

 

[04 commemorative]

Just a followup on the water leak. The dealer replaced the sunroof frame under warranty. It has been four months since the dealer repair and no more water leaks.

Same thing with my 2020Terrain Denali....glad you have no more leaks,hope it's the same for me !

 

[Pistol Pete]

Come on GM. You can do better than this. The large hole in the taillight area was obviously there for a reason but you can do a better job of waterproofing than this. Save yourself some money and fix it yourself. I recommend Flex seal Flex Tape.

 

[dawnbell1030]

I have a 2018 SLT Diesel Terrain with the same problem. The water built up in the spare tire compartment to the point that the water flowed into the rear passenger floor. That's when I noticed the water problem, by hearing the water splashing around. I went outside while it was raining and found water droplets near the aft right rear vent by the hatch (See Pictures). The vehicle is at the dealer and I am waiting on their finding. 2018 SLT Diesel Terrain 21,000 miles

I have this same problem! What was the outcome from the dealer?

 

[dawnbell1030]

So great to discover this thread and seal the tail light body hole with some Gorilla Waterproof rubberized tape. Of course i had water in the spare tire well but see i have a wet rear seating rug. Does anyone have experience that this is also caused by the tail light but have a hard time believing the water traveled there. SO then what is the cause of the next leak, from the roof seam or rear sunroof drain? thanks for any support you may have.

I am also having the same problem with my 2019 GMC Terrain Denali, with water pooling up in the rear tire well, and back seat floor on both sides, but also my front seat floorboards have also been wet when the back isn't, also had A LOT of water condensation on my inside windshield, so I think mine has a few leaks and most likely (from what I've read here in this forum) is from the drain hoses being clogged as well as the tape needing to be replaced behind the tail lights. My husband also noticed long gaps of no rubber weather stripping on top part of hatch, where water can get in and run down towards the inside of the tail lights - poor design of GM. My problem has been going on for almost a year (haven't had money to get it fixed) and my husband just keeps drying it out with fans and shop vac, and using those moisture absorbing pellets in those small containters you leave in the car. So far, I haven't found in this forum if these water issues can cause electrical issues eventually. Even if the factory fixes the problem, I'm concerned about hidden mold that has probably built up by now, and my electronics being rusted or start to have issues from all the moisture for the last 9 months. Not sure if it would be wiser to just trade this in for another vehicle ASAP.

 

[Colt Hero]

@dawnbell1030 : it sounds like you’re all over this water leak problem … reading the Forum and finding the known weak points (the Tape near the Lights, the clogged or disconnected drain line(s) … from a Sunroof?, and maybe even an AC Drain up front?). Now all you gotta do is correct each one. I think these are all DIY fixes, but it depends on what you’re comfortable with.

As far as getting rid of the vehicle … I wouldn’t even think of it (for these very minor issues). To me, you start thinking about dumping a vehicle when the “major mechanicals” start causing too much trouble (which is typically well after 150,000 miles).

Instead, I think a lot of people look for reasons to buy a new vehicle : just made last payment on a loan … just retired … just got divorced … just had another kid … spouse just got one … friend just got one … etc.. Too many automobiles made in this country …

 

[hron61]

^^^ Good post Colt.
Yep, I do love my Terrain, even with all of its llittle quirks.
I've never owned a vehicle that didn't need something or another.
She's a keeper.

 

[joehawthorn65]

I ended up taking my Terrain to my normal independent shop. He said there were two factory cut holes along the pillars of the rear hatch that had some type of tape (like a thicker duct tape) over them that had deteriorated. He said he put a new patch and seal over the holes. It seems to have stopped the water getting in for my case. Honestly I think you'll have to just take it somewhere and have them run their water test to find the leak. My mechanic had my truck for 2 days hunting down the leak. He had to take interior panels off to find out where the water was leaking from.

Right on. tape is the answer. Just remove right rear tail light assembly you will see the taped area.

 

[hubadosx]

hubadosx in s . texas....
i had same problem with myjust bought 2019 slt ...it flooded spare tire well and floor...stench was beyond a cattle feed lot level bad.
dealer took it back ..refunded the full price of purchase.....it was plugged sunroof drain tubes.
hub

 

[evanelliott72]

So it’s leaking in through the brake lights? My friends 2015 gmc terrain is soaked all the way up to the drivers floorboard. The spare tire was a pool of water, we are in Oregon heavy rain, I looked around at the gasket on the doors and, he’s convinced it’s coming from the trunk lid or the tail lights. And now I’m starting to think the same after seeing this post? So take the tail lights off and tape that hole shut or what’s the fix

 

[RIT333]

Very likely that it is leaking thru the rear taillights. Try searching on this forum, and you should find many threads discussing this.