Hello,

2012 Sentra, 2.5L, CVT

The picture below was taken from the engine bay looking up at the wiring harness going through the firewall on the drivers side.

https://imgur.com/ODtki2q

Is there a rubber cover missing from the wiring harness? I'm assuming those wires are not supposed to be exposed like that and that the electrical tape is from a past repair.

I can't find a picture of what it is supposed to look like in a parts catalog or image search.

Any help is appreciated.

Nope, that's normal. The interior portion of the grommet is form-fitted to the wires and waterproof, but because of that it can't be taped all the way to the grommet. The spot where it enters is well-protected against most things (even rodents because there's generally noplace for them to stand), so the small unsupported gap isn't problematic. Most Nissan Engine Room Harnesses are constructed the same way.

Thank you @VStar650CL.

I'm getting water dribbling down the cabin firewall on the drivers side between where the harness penetrates and the brake pedal. This was our next guess for the point of entry.

That would be very unusual. Leaks in that area are almost always from the windshield gasket or a failed body seam between the inner fender and firewall. On a Sentra it's also possible you have a stopped cowl drain and water is overflowing into the HVAC fresh air intake.

Thanks again.

The odd thing with this leak is that we have a difficult time replicating it by spraying the windshield with a hose. It may be that we have only done this test after freshly clearing out the cowl drain and by the time we get a heavy rain it is clogged up again.

-- windshield leak --
We set the air vents on full speed and sprayed water with soap and glycerin along the top and sides of the windshield and didn't get any bubbles. Could the bottom edge of the gasket (under the plastic cowl) be leaking?

-- fender-firewall seam --
I think the seam in the picture below is between the firewall and the inner fender. It was rusty so we put some silicone on it:

https://imgur.com/a/gyYSKjQ

Is this the seam you mentioned? There is a small section of the seam that we couldn't reach before that needs to be sealed.

-- hvac fresh air intake --
Is the HVAC fresh air intake is on the passenger side?

sentra12 wrote: ↑

Tue Nov 02, 2021 6:19 pm

The odd thing with this leak is that we have a difficult time replicating it by spraying the windshield with a hose. It may be that we have only done this test after freshly clearing out the cowl drain and by the time we get a heavy rain it is clogged up again.
-- windshield leak --
We set the air vents on full speed and sprayed water with soap and glycerin along the top and sides of the windshield and didn't get any bubbles. Could the bottom edge of the gasket (under the plastic cowl) be leaking?

When a leak won't respond to dousing with a hose, it often means the water is coming in when the car is driven and wind pressure is force-feeding it. That's very common with leaks in the bottom or sides of the windshield gasket. The only good way to find them is to yank the cowl cover and lower pillar trim and force water up into those areas. Keep in mind that large gaps won't respond to soap-bubble testing, only little ones will.

sentra12 wrote: ↑

Tue Nov 02, 2021 6:19 pm

-- fender-firewall seam --
I think the seam in the picture below is between the firewall and the inner fender. It was rusty so we put some silicone on it:
https://imgur.com/a/gyYSKjQ
Is this the seam you mentioned? There is a small section of the seam that we couldn't reach before that needs to be sealed.

That's one possibility, but also the compound seam where the firewall, inner fender, and A-pillar come together. That can usually be accessed only by jacking the corner of the car and pulling back the rear portion of the fenderwell cover.

sentra12 wrote: ↑

Tue Nov 02, 2021 6:19 pm

-- hvac fresh air intake --
Is the HVAC fresh air intake is on the passenger side?

Yes, but water ingressing there will travel through the blower inlet ducting before leaking into the cabin, so it can show up almost anyplace adjacent to the HVAC.

Good point about large gaps and the soap test.

I should have mentioned in an earlier post that the car is parked outside under a tree most of the week and the only times we have observed the leak is after a moderate to heavy rain lasting >3 hours. It certainly could be happening when it is driven; we just haven't seen it.

I'll look for that seam tonight. The car is currently in the garage with the carpets, under carpet padding, battery, battery tray, and engine air intake tubing (including the air filter and housing, but not including the throttle body) removed.

When we last had the fenderwell cover off we put silicone on the seam (mentioned in the previous post) and removed a large slab of mud from the fender where the cowl water drains out. Pictures of the seam and the mud are here:

https://imgur.com/a/GzeLOxY

That link also has two pictures of where we see the water in the cabin. Interestingly, we don't see any water on the firewall above the two circles in this picture:

https://i.imgur.com/Ab8qWtI.jpeg

Thanks again for the help. We brought the car to a local shop, spent a small pile of money, but didn't resolve the problem. We've gotten far more from this discussion. It looks like this issue, or something related exists for other Nissan models. The folks on this Nissan Versa thread are complaining of similar issues.

The Versas have really under-designed cowl drains. They clog so easily you could call the problem "infamous", so they're a somewhat different story. Your issue, if it isn't the lower windshield seal, is probably more akin to what we see on some Smyrna Rogues. There's a bulletin about those, it will give you a good idea what I mean about seams:

https://static.nhtsa.gov/odi/tsbs/2021/ ... 2-0001.pdf

The recall notice gave me a good idea what to look for. Thank you.

I pulled back the plastic fenderwell cover on the driver side and took a bunch of pictures.

https://imgur.com/a/O63Ko2N

I didn't see any seams that were obviously missing sealant. The metal support/gusset attached to the fenderwell with rust along the edges looks 'bad', but the rust doesn't appear to be deep enough to penetrate through the firewall.

Assuming I didn't miss a bad seam, then I'm thinking the next step will be to run the soap test again on the bottom of the windshield (the wipers and plastic cowling were also removed last night).

Thanks again.