Ok, I bought my car used a couple of years ago. It was in flawless shape, one-meticulous owner before me. Full service book, everything done by the dealer, no collision reports. The only issue it had when I bought it was the rear passenger footwell was damp, and the dealer (probably) lied saying it was probably still damp from being shampooed/detailed.

I live in the PacNW where it rains a lot, and I don't have a garage. My car is outside 24/7.

Water is getting in somehow, and pooling in the rear left passenger footwell. But I don't know how it's getting there.

There are no water stains and no dampness around the sunroof, the windows, or the door seals. The pooled water is ONLY in that one area. It isn't in the driver's footwell or the right rear footwell. The trunk is dry.

How much water is in there? Enough that when I removed the rear floormat and hung it in the laundry room it literally dripped for an hour.

Anyone have any ideas where it might be coming from? Are there drain plugs or anything in the floor that may have come loose? Anyone have a similar issue?

 

If door seals are good then next thing I'd look at is the sunroof seals. I skimmed thru this thread, I'll link it towards the end, that the sunroof seals sometimes let water in when closed and there are drain tubes that run down the four pillars that tend to get clogged. I'd suggest you lift your carpet from where it gets wet and have someone help you out by spraying water on your car with a hose while you inspect the car from the inside to narrow down where it's coming from. Also be sure to dry your mats and carpet thoroughly before you start getting that moldy smell. I also recommend you buy a DampRid bucket and leave it in your car to get most of the moisture out, helped me big time when I left my sunroof open overnight during a thunderstorm. https://g35driver.com/forums/g-spot/...-solution.html

 

Well, I dropped the headliner in my G35 sedan and the sunroof drain hoses are intact and working properly. I confirmed by free pouring water in the channels and all of the hoses flow the same - no obstructions, no leaks. No evidence of water in the area of the sunroof at all.

So that's not the cause of the water accumulating in my rear passenger foot well. Anyone else know of any likely causes?

 

SOLVED!

Ok, this leak was driving me insane. The last straw was when I had to leave my car parked for a month in November (heavy rain season) and found 2" if water pooled in the rear left foot well. So much water that it filled half the shopvac.

After checking the windows, sunroof, and sunroof drains for leaks and finding none, I then turned to any other sources of water coming in from the rear: trunk seals? No, they're fine. Rear door seals? Also fine. Tail-light gaskets? Fine. Under the car, any evidence of water getting in from below? Nope.

I admitted defeat and took it to a glass place to do a compression test on both the windshield and rear window seals. I don't have a compressor at home so I had to take it elsewhere.

The windows checked-out fine. That's bad news, right? Well, it is sort of bad news. The good news is the guy at the glass place just happened to notice a little trickle of water in the drivers floor mat after spraying the windshield. Since the windshield passed inspection he took a closer look under the dash. Everything on the firewall looked fine..... except one little leak which was almost invisible unless you hold a bright light right next to it.

The culprit is a little boot that covers the area where the clutch pedal passes through the firewall.

The good news? It's $16 in Canada (probably around $12 in the US) and can be changed without getting between the engine and firewall - it attaches on the interior side of the firewall.

The bad news? It's not commonly stocked by Nissan North America. So it'll be a three week wait before it arrives from Japan. So I guess I'll just have to keep bailing.

Part number is: 30653U

For those with the same mystery leak on your 6MT G or Z, start in this area. I was fooled by the water in the rear of the car because my driveway is on a very slight incline and gravity drew the water away from the source of the leak.

 

Glad you finally found it!!!

 

So... It was a boot UNDER the hood? How was water getting to the boot? Or was it coming in from the vents by the wipers?

 

I haven't gotten into it yet since the part is on backorder. The boot attaches on the inside (interior) of the firewall. Water is getting under the hood and running down the firewall. Once I get in there I'll be using silicone anywhere it looks like it could help.