Water under cargo area floor

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bobkart

Well-known member
Joined
Dec 22, 2018
Messages
346
Location
Pacific Northwest
A while back I was poking around in the cargo area and noticed water under the cargo floor. Removing the cargo 'floor' piece revealed a round black plastic plug, towards the rear and just right of center, a couple of inches in diameter, that seemed to be letting water in from below. Possibly this plug is meant to let water out, should any get into the cargo area. Removing that plug revealed an empty space above the rearmost under-body panel, which the rear bumper attaches to (where a spare tire might go). I explored a bit more to see how water might be getting into that area from below and found that the rear bumper was missing a couple of clips to attach it to the under-body panel, which allowed it to sag down, nearly an inch in places, and act as a scoop for water being kicked up by (for example) the rear tires. At least that was my theory, and I picked up the necessary clips and installed them, which closed the gap nicely.

Fast forward to a few days ago when I had the idea to check under the cargo floor again, having driven through puddles a fair bit earlier in the day. There was still water under the cargo floor, although not as much and more towards the left instead of close to where the round black plastic plug is. I feel like, with the way that the rear bumper overlaps *below* the rearmost under-body panel (instead of above), there could still be some water-scooping effect of that seam. I'm tempted to run some racers tape (leading-edge/helicopter tape) across that seam and repeat the experiment. Wondering if anyone here has any similar experience, with water getting into the area under the cargo floor, and/or theories as to how it might be happening.

While I'm in this area, early on I noticed that just above the rear license plate is just an open space, nearly large enough to insert a hand. The opening faces downward, so is probably safe from rain entering, but it seems odd. Wondering if it's just my Leaf or if others also have this opening.

I can take and post pictures if that will help . . . here is one from the Underneath the Beast thread that shows the area in question from below, with the rearmost under-body panel removed:

IMG_0688.jpg


Those holes in the rear bumper (red part) is where I was missing a couple of clips.
 
cwerdna said:
Maybe what you're experiencing is related to http://www.mynissanleaf.com/viewtopic.php?t=19373?
Thanks for the reply. I had looked that thread over before making this one; there doesn't seem to be much symptom overlap as I have no moisture in the back seat area . . . that I'm aware of . . . I'll check more closely tomorrow.

Can you weigh in on the gaping hole above the license plate recess? Wanting to make sure that's normal, that I'm not missing some trim piece that closes that up.
 
I found a better picture of the potential problem area (not my Leaf)

mBctSY6.jpg


Note how the rear bumper overlaps below the under-body panel, such that water kicked up by the rear tires can get into the seam. It's especially obvious on those downward 'vanes', where in this picture it looks like there's a substantial gap, maybe as much as half an inch.

Wondering if anyone else is seeing water under the cargo floor that might be attributable to this bumper/panel interface.

Also, I found a thread that answers my question about the hole above the license plate recess: https://www.mynissanleaf.com/viewtopic.php?p=80853
 
I don't think that the bumper is 'scooping up' water unless it is damaged and you are driving through standing water. That plugged hole in the cargo area, BTW, is common with many cars. I think it lets paint drain from the area during paint application at the factory. I used it to secure a spare tire (with a J bolt through the grommet) on my 2013.
 
Did you manage to resolve this issue as I have just noticed the same thing under my cargo area ?

G
 
Grazee said:
Did you manage to resolve this issue as I have just noticed the same thing under my cargo area ?
This is still an open question in my mind. I get the impression that spray from the tires hits the little openings formed around the diffuser strakes where they transition from the black lower cover to the rear bumper (white in my case). Those openings are large enough to get part of a pinky finger into. They really should have overlapped that the other way (leading part covering the trailing part).

Now that I have a GoPro camera, I've been considering setting it up in that area in an attempt to confirm water coming in via the mechanism I suspect.

Another action I've contemplated is covering those opening with racers tape. But I'd need to be able to repeat the problem at will (to be sure that fixed it), and it doesn't happen predictably enough for me to have confidence that not seeing moisture in the problem area proves I've fixed it.
 
Hello Bobkart

Did you find a solution on the water entrance?

I really need some help on this.

Just found water under my cargo area floor.

The insulation padding was wet like a kitchen sponge... Now what to do?

I have a picture of it, but cant upload it..
(Please see enclosed picture. Do you think the water came from the area the arrow point at - that the tires spray water into the cargo area.)

There is no water on top of the cargo cover - all dry.

Best Regards

Julie
 
Hi Julie, I've been meaning to try to get video of water splashing into that area below the luggage 'deck'. Just have been too busy with more important things.

You can add an image to a post by uploading it to an image-sharing website (like Imgur) and including a link to the hosted copy of the image in your post.

One less-involved approach to narrowing down where the water is coming from that I came up with is to tape a strip of (say) paper towel so it hangs partway into the area in question (there a round black plastic plug that you can remove to see into that area). Maybe start with the paper towel strip nearly touching the bottom of that area. Then drive through puddles 'at speed', or whatever you think might be causing the problem, then check the paper towel strip for moisture. Granted this isn't as definitive as video of the water coming in, but can help confirm/deny the hypothesis.
 
Thank you Bobkart

Yes, I thought of it too. I am planning to put pieces of pink cleaning cloths in all small 'caps' where my fingers can get in between.
Tomorrows forecast shows rain here in Denmark and I'm up for a ride through puddles.

I also suspect it is spray from the tires that gets the water inside the cargo area under the cover.

SbqxN3q


What would you recommend to caulking/tightening the caps with?

Thank you in advance and happy easter.
 
Here's the picture that JulieHolm tried to post:

nUvj1Bd.png


Your water is more to the sides than I tend to see. Mine is more towards the very back. But could still be the same basic cause.

For clarity, my suspicion is that water can enter the small gaps between the rear bumper and the lower rear body panel:

Ge1v2HE.jpg


My opinion is that they got the direction of overlap wrong there: the more forward piece should overlap *outside* the trailing piece, to avoid creating a 'scoop' effect with the gap formed by the overlap. I'll bet even setting aside moisture intrusion, there would less aero drag with the overlap reversed.

What I'm less clear on is how water gets from the area under the cargo floor into the actual cargo area. But if the spray from the rear tires is forceful enough, there could be enough leftover momentum in the water that makes into onto that area to continue intruding upward. I know it sounds a bit far-fetched, but it's the best theory I have. Clearly if that area is initially dry, and it's not raining but the roads are wet, and you take a drive (and hit some big puddles) and that area is now wet, it had to have come from below. The exact mechanism is more of a question for how to remedy the problem.

P.S. Happy Easter!
 
bobkart said:
Your water is more to the sides than I tend to see. Mine is more towards the very back. But could still be the same basic cause.

For clarity, my suspicion is that water can enter the small gaps between the rear bumper and the lower rear body panel:
Is your Leaf a 2018? The reason I ask, the way it is sealed in that area looks completely different than mine (2020), but I've checked mine after the great flood we just had here and no moisture or water anywhere.

oicHxtX.jpg
 
Mine is a 2016 . . . the first picture I posted is a repost of what JulieHolm tried to post. I think even the newer generation Leaf (2018+) still has that (what I consider) flaw (reversed overlap between rear bumper and lower panel).

One other potential explanation that comes to mind is the moisture entering through that large opening above the rear licenses plate . . . does your 2020 have that?

It might be that the problem has been addressed somewhere between 2016 and 2020. If we knew what that change was, we could better understand the problem.
 
Have you ruled out any possibility of water coming in from above and running out under the plastic panel to the right of the arrow, e.g. the seal around the glass or the rubber seal for the trunk lid?

There is a outlet vent in the area above and to the sides of the opening for the license plate, if the rubber flap has been torn or jammed then it might be another path for water (and rodents).
 
bobkart said:
Mine is a 2016 . . . the first picture I posted is a repost of what JulieHolm tried to post. I think even the newer generation Leaf (2018+) still has that (what I consider) flaw (reversed overlap between rear bumper and lower panel).
Ok, I was going by your delivery date in your profile, so you have a Gen 1 Leaf. I don't have mine anymore, but I can say that on the Gen 2, that area where the overlay is, there is no path I could see to get inside. I had to take off my rear air diffuser recently to install my trailer hitch and while I had the thing off, it is just a big gap back there (well, the Gen 2 has the sensors for the rear, so there is wiring for that), but unless the water is being rammed up into the rear to make that gap and getting through, the way it looks on mine anyway, seems you would have to be river driving to get water to come in back there.

One other potential explanation that comes to mind is the moisture entering through that large opening above the rear licenses plate . . . does your 2020 have that?
I know exactly what gap you are referring to, I used that to the hide cords and plug for my trailer hitch lights (My Gen 1 also had a trailer hitch :mrgreen: ) Unfortunately, that gap is gone in Gen 2, so wiring up my new hitch and finding where to hide the plug and cable is another challenge. :?
It might be that the problem has been addressed somewhere between 2016 and 2020. If we knew what that change was, we could better understand the problem.
You've got the best resource here to find out, lots of models and people that can post up pictures to see the difference at least. :)
 
Hearing that the big opening above the license plate is gone with Gen2 and also that Gen2 isn't seeing this problem (less sure on that), to me pushes that opening much higher on the list of suspects.

On the one hand it seems like an easy position to take that 'water can't get in there while travelling forward' because the airflow should all be away from the rear of the car. But we've all seen examples of airflow that doesn't obey simple intuition, like exhaust gases getting into the slightly-rolled-down rear window of the old station wagons (while underway).

Another clue that this opening could be the problem is that they plugged it in the next generation.

I think that opening can be accessed from the inside by removing the handful of trim pieces on the inside of the hatch. I've had them off a time or two, but didn't think to look for that opening. Even from just the outside, a simple experiment could help answer the question, like taping a piece of cloth or paper towel over the opening and taking a drive in the rain. A more serious test would involve really blocking that hole from the inside and periodically checking for moisture in the previously-affected areas over the course of the next rainy season.
 
My 2014 Tekna also gets a wet floor in the boot/trunk. It doesn't happen with rain when the car is stationary nor does it seem to happen in wet driving, but if I rinse off with a garden hose after washing the car and I am too enthusiastic with where I spray around the tailgate area, water comes in where the floor disappears under the plastic panel in the luggage area rear (i.e. nearest the rear of the car), so I assume there's a seal not doing its job somewhere around where the bumper moulding meets the steel floorpan. My answer is to avoid washing it!
 
Water is likely not ending up there at all via under as the grommet plug is it is precisely to there to prevent that. The likely scenario is your hatch seal, or taillight wiring grommet. Remove both rear taillights and check this.

Also check the wiring grommet in the forward/driving side area of the cargo floor (it goes under the car) and make sure it is sealed. If you have a sub (and I call it that loosely, ha) remove the 3 x 10mm bolts and connector to completely remove the floor panel.

Bob, the issue with overlap on the lower chassis shield is a zero issue. The cabin floor is nearly 12 inches above that shield and is not connected in any way. I can take a few pics as I have all that stuff removed right now on my 2018, but I promise you that is not your issue :)
 
denwood said:
Bob, the issue with overlap on the lower chassis shield is a zero issue. The cabin floor is nearly 12 inches above that shield and is not connected in any way. I can take a few pics as I have all that stuff removed right now on my 2018, but I promise you that is not your issue :)

Thanks for weighing in. I understand that position. I do believe that water can get scooped up by that overlap (spray from rear tires or splashing from puddles). I believe your point is that the vertical distance is too far for any water that gets in that way to make its way to the cargo area floor. I do admit explaining that is tougher. I know it's a long shot but if the intruding water spray has enough leftover momentum, it MIGHT make it up to the area in question. I'm definitely not sure that's actually happening, but have that on the list of suspects.

With the recent above discussion, my focus has shifted to the large opening above the license plate, then a kind of backdraft effect that can draw trailing mist in as the vehicle moves forward. It then drips down and gets onto the cargo area floor from the rearmost portion of the cargo area (where I typically see water when I do).

If you don't think it can be either of these mechanisms, do you have a theory? We know water is getting in, and most people are fairly certain that it's not coming from above (by just being rained on).
 
You will need to see about removing the rear plastic panels to inspect the one-way exhaust vents in the rear of the trunk to either side of the license plate opening. It has a flimsy rubber flap that mice can chew and get in. If the flap is damaged, bent or torn then it is a direct opening to the trunk behind the plastic panels.

s-l640.jpg
 
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