asawyer97
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I discovered about 2 weeks ago that the rear passenger footwell was filling up with water and soaking the carpet in my 2020 GT Coupe. Shortly after, I also found that the passenger side of my trunk carpet was slightly damp as well. After a couple weeks of tracking it down I have finally found the issue and I thought I would share in case anyone else has been unable to find the source of water intrusion.
Initially, I thought the water intrusion was due to the body holes in the A-pillar that Ford put out a TSB about a few years ago. The tape for those were gone in my car but even after I had sealed them with rubber grommets, after the next rain storm, I had even more water in my passenger footwell.
After that, I decided to check the cowl drain locations. Both the drain under the battery tray and the (harder to get to) drain underneath the cowl cover were both clear.
I found that one of the holes in the body used to connect the passenger side of the cowl did not have a plastic retainer in it and that could possibly cause water intrusion as it was also on the passenger side A-pillar just below the windshield. I temporarily covered this hole with another rubber grommet just to be sure no water got in that way.
Finally, I decided to remove the entire passenger side of the interior, both to dry it out completely, and to see if I could find the source of the water intrusion.
Well, after about 20 mins of rain, I finally figured it out.
This is a picture of the passenger quarter window and the circled part is one of the connectors for the plastic trim holding the curtain airbag. Water was dripping from this spot both during the rain, and after subsequent tests the next day with a garden hose.
The blue lines are the path that the water took from the passenger C-pillar to the rear tire well, then to the rear passenger seat pan and towards the front of the car.
I can only assume that the water pooled in the rear passenger seat pan for a long time, because only about 10-20 mLs of water got in during a ~45 min rainstorm.
Best I can tell, the water flowed through a hole in the crossmember (filled in circle at the top of the previous picture) and soaked the rear passenger footwell. Driving the car with the water likely exacerbated the issue because every time you brake, the water would move towards the front of the car and soak more of the carpet.
Water eventually got to the front passenger footwell but luckily did not seem to get near the BCM or affect anything in that area. Most of the water I saw in the cabin was concentrated in the rear of the car but the front carpets were definitely damp.
The rear trunk was also wet after this storm and the water appeared to be dripping from the interior of the rear quarter panel (the top blue circle in the next picture)
Water then pooled on the sound deadening and flowed to the right, underneath the tail light.
The two points that I saw water dripping from on the interior were both connected to the same piece of metal. It seemed to run along the interior of the roof line but some of the water dropped through the connection point for the airbag and some continued through to the trunk.
After some further testing with a hose, I found that the intrusion was somewhere in the area covered with the red line, along the gap between the rear windshield and the body panel. I could not find a spot where water was getting through the windshield glue but I did see the a very small hole, about 1/16th of an inch in the very corner where the roof meets the rear quarter panel.
I ended up sealing the area in red with the windshield and glass sealant from Autozone (the orange tube) and, after letting it cure, I water tested again and finally had no leaks. The sealant says it dries clear but has a slight opaque look to it which looks pretty bad when extra bits get on the paint or glass. Luckily it is super easy to scrape off with a plastic tool of some sort as long as you go gentle on the paint.
I will update this if the fix ends up not holding or something new appears but, as of now, this time spent on this job was 99% finding the issue and 1% fixing it. Hopefully if anyone else runs into this issue they can just skip the 99% and fix the leak quickly.
edit: Also wanted to add that none of the water leaking in was visibile on the windows or interior panels. It all happened behind the trim so the only way to find the leak was to pull all the trim out of that side of the car.
Initially, I thought the water intrusion was due to the body holes in the A-pillar that Ford put out a TSB about a few years ago. The tape for those were gone in my car but even after I had sealed them with rubber grommets, after the next rain storm, I had even more water in my passenger footwell.
After that, I decided to check the cowl drain locations. Both the drain under the battery tray and the (harder to get to) drain underneath the cowl cover were both clear.
I found that one of the holes in the body used to connect the passenger side of the cowl did not have a plastic retainer in it and that could possibly cause water intrusion as it was also on the passenger side A-pillar just below the windshield. I temporarily covered this hole with another rubber grommet just to be sure no water got in that way.
Finally, I decided to remove the entire passenger side of the interior, both to dry it out completely, and to see if I could find the source of the water intrusion.
Well, after about 20 mins of rain, I finally figured it out.
This is a picture of the passenger quarter window and the circled part is one of the connectors for the plastic trim holding the curtain airbag. Water was dripping from this spot both during the rain, and after subsequent tests the next day with a garden hose.
The blue lines are the path that the water took from the passenger C-pillar to the rear tire well, then to the rear passenger seat pan and towards the front of the car.
I can only assume that the water pooled in the rear passenger seat pan for a long time, because only about 10-20 mLs of water got in during a ~45 min rainstorm.
Best I can tell, the water flowed through a hole in the crossmember (filled in circle at the top of the previous picture) and soaked the rear passenger footwell. Driving the car with the water likely exacerbated the issue because every time you brake, the water would move towards the front of the car and soak more of the carpet.
Water eventually got to the front passenger footwell but luckily did not seem to get near the BCM or affect anything in that area. Most of the water I saw in the cabin was concentrated in the rear of the car but the front carpets were definitely damp.
The rear trunk was also wet after this storm and the water appeared to be dripping from the interior of the rear quarter panel (the top blue circle in the next picture)
Water then pooled on the sound deadening and flowed to the right, underneath the tail light.
The two points that I saw water dripping from on the interior were both connected to the same piece of metal. It seemed to run along the interior of the roof line but some of the water dropped through the connection point for the airbag and some continued through to the trunk.
After some further testing with a hose, I found that the intrusion was somewhere in the area covered with the red line, along the gap between the rear windshield and the body panel. I could not find a spot where water was getting through the windshield glue but I did see the a very small hole, about 1/16th of an inch in the very corner where the roof meets the rear quarter panel.
I ended up sealing the area in red with the windshield and glass sealant from Autozone (the orange tube) and, after letting it cure, I water tested again and finally had no leaks. The sealant says it dries clear but has a slight opaque look to it which looks pretty bad when extra bits get on the paint or glass. Luckily it is super easy to scrape off with a plastic tool of some sort as long as you go gentle on the paint.
I will update this if the fix ends up not holding or something new appears but, as of now, this time spent on this job was 99% finding the issue and 1% fixing it. Hopefully if anyone else runs into this issue they can just skip the 99% and fix the leak quickly.
edit: Also wanted to add that none of the water leaking in was visibile on the windows or interior panels. It all happened behind the trim so the only way to find the leak was to pull all the trim out of that side of the car.
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