Re: 2012 GMC Terrain SunRoof Drain Issue
If you can blow through it, its possible it's not the cause of your leak. Start with a cup and slowly pour a lot of water down the drains. If it drains quickly (and there is nothing in the car) it's probably something like a body side seal.
It also helps to go a manual carwash and spray it down while watching/feeling inside. A sunroof will leak, that is why there are drains, but it shouldn't leak that much unless it's broke.
You'd have a have a hole in the drain tube for the water to drain, but still flood the car.
2017 Equinox 3.6L Premier AWD
2011 Silverado 1500 LT, 5.3L 4X4