Have a 2010 GMC Terrain, with a bad water leak in the floorboards of both driver and passenger side front seats. Leaks when it rains and car is stationary. No noticeable damage to the weatherstripping or anything, it isn't leaking out of the sunroof. I've never really had to hunt water leaks outside of weatherstripping. Any good pointers or ideas as to where I should be starting? I work on bulldozers for a living, so little passenger cars is a bit out of my normal realm of operations.