OK, so the G37 had the infamous sunroof drain issue and I had fixed both the driver side and passenger sides. However, I still noticed water intrusion in the passenger side when the rain is heavy. A light rain does not show a leak. The leak comes from the side closest to the door and depending on the amount and rate of rain, can be anything from a drip to a thin stream. The issue was driving me mad, as I looked at where the water was coming in at. The lower windshield, where the cowl of the hood meets (under and around the wiper arms) seem to be loose and not sealed or tightly up against the car. I took the cowling off and saw where most people state is the second most prevelant location where water comes in, the air filter duct seal and the surrounding area by the battery. So I basically went crazy with RTV silicone in hopes of blocking off and sealing all avenues of where the water might come in. Well that seemed at first to work. But then, upon a midnight dreary, a raven came a knocking on my door... no... no sorry wrong issue. No a particluarly heavy downpour came by at night and at first I did not notice the leak, until I moved the car by backing out of my driveway. That action moved, I guess some water that may have pooled behind the interior pocket of the glovebox and water came dripping out. Great, now where the Hell is this coming from?!? So I basically did a water test, when things warmed up a bit recently. I could not use a hose as the water lines from my well were still offline. But I did a bucket pour of water slowly over the sunroof and top of the car by the passenger door. Not so much as to be like a dive into a river. But enough to "speed" up the process of finding the leak. Sure enough, when pouring the water at a particular area, I got the leak. So I stopped doing the water test and reviewed the are that the water appeared to have gone through. Below are pics of the area. It is essentially the weather stripping along the bottom side edge of the windshield. Instead of sitting snugly against the car laying flat and sealed. The stripping appears lifted and sure enough, I can raise the end up to show how the water can get down behind the battery and find something to get into the dash. The area that should be dry was wet and now, after all this. What can be done about this weather stripping? I am not sure how it is applied, what it connects and extend to under the hood and cowl of the car. To remove it, means removing what else? To RTV it, may or may not work as it appears that it should be lying flat against the glass and car. RTV will just keep the strip raised and maintain a deformity of the seal elsewhere, letting water through just at a different location. Has anyone every had this seal replaced? What did it involve and cost? Was it a body shop or a windshield shop? The pics below should help with these questions. The one pic shows the driver side which is how it should look and the rest are from the passenger side. The area is up above the far left corner of the battery location. Thanks to anyone who replies back, in advance.

 

Remove the lower dash cover (under the glove box) and check for water/ evidence of water straining. Also, take the time and thoroughly check the cabin air filter for signs it has been getting wet. Once the cowl seals deteriorate water just flows under the cowls and onto the firewall. There are only two (2) possible ways water can enter the cabin from that location: the fresh air intake and the wiring harness. Unless your windshield has been repaired I doubt the butyl seal from the factory failed. This, along with new cowls, solved my leak issue 100%.

As you have a sedan I would rule out the door seals as it seems only the Coupe's with the frameless windows develop leaks in that region.