It's been a long time since I've been on here; I still have my '08 S after 15.5 years and 132k miles later. It's been the fourth car in the stable for quite some time now, so it's been relegated to sitting outside.

Long story short, I recently discovered a lot of water in the trunk but have no idea how long it's been there. First, there was water in the spare tire well area, which has since been drained and I'm currently not finding any more water there again. However, I'm seeing water consistently in the passenger side cavity where the air flow/pressure vent is. I've extracted the water out several times now, but keep finding water there. During a quick troubleshooting session, I had my daughter take a hose and spray water directly into the "gap" where the rear bumper cover meets the rear quarter panel and do see water coming through the aforementioned air flow/pressure vent. However, that doesn't seem like a natural way for rain/water to enter? With that said, we could not get or see any water make its way to that cavity by any other area or means during our limited testing.

Does that cavity area have some sort of drain that is clogged, and it's not allowing it to drain? Or is there another drain for some other area (e.g, rear sunroof?) that is missing or clogged and diverting water here as a result? Or perhaps I have a leak somewhere? Any thoughts or insight would be greatly appreciated. I don't have much time nowadays so I'd like to have a plan of attack before tearing the car part.

I was thinking of removing the rear bumper cover and potentially replacing the air flow/pressure vent (I assume it's replaceable and relatively cheap?), even though it doesn't make too much sense to me for water to enter that way naturally.

In the meantime, my driveway has a very slight slope or grade so I started backing into the driveway so water can try and flow away from the trunk area instead of towards it.

 

empty out the trunk, let it dry and coat the inside with baby powder. static will make it stick.
this will let you track the path of the water before you start guessing what it is.
you can try an automatic car wash next to see if you can find the path.

there are several ways water can get into the trunk, so you would be replacing, or tearing a lot of stuff apart guessing.
if you start at the top, you have the trunk seal itself.
working down you have the tail light seals.
then you have wicking from the carpet into the back. had that happen due to the sun roof drain hoses not being reattached properly.
blocked hoses for the sunroof
there are also supposed to be drains near the trunk extensions bellow where you show your picture on some cars. not positive for these.

 

Sunroof drains, IF you have one. I bought a 2007 Sedan V36 and it had water under front seats and in the trunk from the plugged up 1mm hole sized drains. Did a tube bypass into AC drain and no more water. But then again, I keep my car inside the garage. But, after a decade, it's normal for sunroofs to leak; Seals crack, moldings get brittle, it's sagging, drains get plugged up (yes folks, sunroofs require maintenance!).

This is what i've used: , . Remove both front side upper pillar covers by pulled them off from their clips and there you will have black drain tubes. Cut them 8-10" away from the dashboard and route the 3/8 tubing to the AC drain using the photo for reference. ALSO, before you do that, confirm the black OEM drains are attached to the sunroof drain pan, mine came off on driver side completely.


Sunroof drains on 07 G35

uTube that and there are plenty of videos on how to do it. And if your car smells like mine did after baking in the florida sun for few years, then get this: . Two 10 minute sessions with this and trust me, no smell of mold, mildew, cigarettes and any other bodily secretions scents, just plain ozonated air.

 

I thought I would provide a quick update. In short, the air flow/pressure vent was indeed the source of the water leak. I incorrectly assumed, but with the car at an incline, water does naturally flow to this area as pictured below.

After realizing I had ordered the wrong part number when removing the rear bumper cover, I uninstalled and reinstalled the original part and did my best to ensure it was fully seated. I then used some molding tape I had laying around to provide a “awning” of sort to divert the water away from entering.

All is well, at least for now.

 

That's the problem with Nissan, they use cheap plastic parts that shrink with heat from the inside of the car. My dash panel shrank in many places, plastic mouldings changed shapes and the front left sunroof drain tube shrank inside the pillar and came off of the upper drain. Run a water test using garden hose at low pressure, jam it to each drain hole to flush out any dirt and make sure it's draining on all 4 corners before it fl00ds your carpet again.

 

A stiff, heavyweight fishing line is a good "tool" to use to rod out the sunroof drains. Just be careful you don't dislodge the drain from the nipple at the sunroof when pushing into the drain....