My Cobalt's been sitting outdoors for a while waiting for some work to be done. Yesterday I went to get started and found my driver's side mat and carpet completely soaked. I cleaned that all up and couldn't spot any obvious leaks. Door seal looks good, no standing water around the sunroof. Last night it started raining heavily into today. So while it's raining I hopped into the car and found a the foot well carpet completely saturated and visibly saw water leaking down the left side kick panel (see picture). I tried looking up under the dash to see if I could spot the water but with the soaked, it being 50F outside and still pouring I ended my investigation. I was wondering if anyone had any idea where this could be leaking from?

 

The culprit is usually a clogged sunroof drain. It won't have standing water if it's draining into the cabin.

 

I've had the car since new and never had the sunroof clog; though, I was hoping it was just that. It seems like an odd place for the leak to reveal itself, which concerned me. When I've had sunroof drains clog before I've generally been greeted with cold water down my back when I hit the brakes so I suppose this is an improvement.

 

Water is a funny thing. I am a roofer and a leak can be at point B as to where you are seeing it wet, but point A is where its actually at and running to point b. I also would suspect the sunroof if the door seal looks good. Its very unlikely that the door seal is bad. What you can do, is water the windshield first see if its leaking, move to just the door. Avoid the sunroof. Then move on to the sunroof. When you water the areas of potential entry make sure you are simulating a hard rain. That is how we often times find a hard to find leak. You can use your sprayer on a water house.

 

MK4 Volkswagens were notoriously bad about this - and I owned one that eventually had this problem. VW had put little rubber nipples at the ends of the drains, over many years, dirt and debris would build up and eventually, water started to back up and you'd have wet carpet in the front footwells (the rear drains caused your headliner to be wet/stained). The second issue, is that the tubes were typically made of multiple pieces and the joints were simple slip-fit, so when water backed up, it'd leak out of the slip.

I honestly don't know much about the Cobalt's sunroof drains and their locations... but based on my VW experience, I'd look for the drain first to see if it's clogged up.

Second line of business would be to make sure you get that cleaned/vacuumed up real well. Mildew is not fun.