So, I've just discovered my car is taking on a bit of water inside. I found a treasure under the cowl.

I've had my 07 Cayman Base for just about a month now, and have noticed the windows are consistently foggy inside after it's sat for a night. At first I thought it was a combination of pretty much 100% humidity every day and leftover moisture from the carpets getting shampooed at the dealer. Reached under the passenger floor mat today to fish out a USB cable for my phone and found the passenger side carpet is soaked . Pulled the foam trim piece from under the glove box and removed the small end of the drain tube from what I can only imagine is the HVAC blower housing. Dry, doesn't seem to be coming from there, at least not at the moment. Then I went up front and checked the area around the battery under the cowl and took a look at the air filter. Was running out of light and time considering it's valentines day here, but I found this: Something tells me it may have something to do with my problem. Will pull it out in the AM and update. Filter didn't want to move, I think it's frozen on as it's all of 20 F here today and the filter felt wet. This may be a fun experience - that nest looks like it's been there a while. Thankfully, whatever made it didn't eat any of the conveniently close-by wiring.

That’s one of my biggest worries - rodents getting to my car in winter. A few winters ago a mouse started to build a nest in my exhaust thankfully I caught it time before any damage was done. Now I put glue boards, moth balls and dryer sheets all over my garage and haven’t had a problem since. ‘’Hopefully there’s no permanent damage to your car.

Motherf....so, I found I dryer sheet next to the air filter when I opened it up. Didn't know they could be used as mouse deterrent. This makes me think PO knew there was a rodent issue in their garage. And that my Porsche dealer needs to be more observant - I highly doubt this happened in three weeks of daily use. I'm gonna scope it out more in the morning. Doesn't seem to be anything permanent, I think whatever was in there just made a mess of the cabin air intake. It also seems to have eaten through the flap over the filter itself, which is possibly letting water into the HVAC system.

FYI - some people don’t believe the dryer sheet works - some have actually said the mice used it as bedding. When I store my car for winter I place a few dryer sheets in the trunk, frunk and a few on the floor in the interior. I scatter mothballs all over the garage floor and especially near the tires , front lip and exhaust. since I’ve been doing this I haven’t had a single issue or any evidence of rodents in my garage.

She won't get stored - I'm dailying this beast, all year round Previous owner only put like 20k on it over about five years according to Carfax and the few service records I have in my possession, so it had to be stored a decent chunk of the time. Likely the root cause. That said, I just got the old filter out. Wet, and absolutely filled with what looks like carpet padding or insulation. Not only did the little buggers eat the flap that hangs over the front of the filter, they ate a decent amount of the hard foam cover that keeps water from running in. Hence the liquid presence. Good news - they didn't eat the filter itself so aside from visible water under the fan, it's perfectly clean in there. As cold as it's been here the last few days, my best guess is that water was just continuously pouring in and when it got cold enough, froze and plugged the drain (and or was seeping around the grommet in the front bulkhead where the intake meets the fan housing). New filter shows up at O'Reilly in a couple hours, ordering a new foam cover from Pelican or somewhere, in the meantime going to Jerry-rig a cover out of an Amazon Prime bubble mailer that conveniently showed up this morning and is exactly the right size

I love it. “ in the meantime going to Jerry-rig a cover out of an Amazon Prime bubble mailer that conveniently showed up this morning and is exactly the right size ;” Glad u caught it in time before they got to the wiring.

Indeed! Little guys are long gone, thankfully, and somehow they didn't so much as touch the bigass wiring loom that runs right next to the filter box. Nor did they pack any of the cowl drains with crud. Looks like I got off pretty light, all things considered. Although now I want to pull the engine cover and check the air intakes for similar attempts at rodent homemaking. PPI was pretty clean, but I don't know if "mouse infestation" has a checkbox on their work sheet. Added bonus, the blue Amazon uses on the packaging should go really nicely with the car's Cobalt Blue bodywork!

Bask in the glory. Should hopefully keep rainwater at bay until the replacement cover comes in.

LOL nice MacGyver! I am amazed they didn't go for the wiring, you're very lucky on that score.

Right? Wiring is clean, praise Jeebus. The only electrical issue is the damn ASK amp for my door woofers not working, but the wiring and fuse for it both look just fine so I can only imagine the known-to-be-janky, Italian-made amp is in fact, completely dead.

A few days, a bit of rain, and a car wash later, this was definitely my problem. Amazon 's bubble wrap is doing the Lord's work for me while I get the real parts ordered and shipped. At the very least I don't have to wipe down the inside of the windows before I get moving in the AM anymore, and the passenger floor is bone dry.

Have the same exact problem as OP -- mice had used my cabin filter as a toilet, and the foam cover is ripped. I didn't realize that had a waterproofing function, is this water that comes down from the windshield and is then supposed to be redirected down to the cowl, over the filter?

They nibbled away the part of the lower foam housing that redirects water coming down from the windshield into the tray (where it can then drain out). They ALSO ate a big hole in the flap that hangs down off the cowl trim. From looking at the way it all goes together, I think the flappy bit isn't doing as much of the work as a lot of the water is going to seep in under the plastic cowl trim piece, thus avoiding the flap. I never did get around to ordering a replacement, so I'm still rolling with that bit of bubble mailer wedged in there. Somehow, this has held up just fine for almost a year - thanks, I guess, Amazon ?

So I think this might be why I have a bunch of water underneath my passenger carpet…

Ooof, yeah, that's pretty similar to the shape mine was in. There's supposed to be a continuation of that elevated lip on the lower foam piece - water's just gonna dump right onto the filter with that chewed off.