The seal is there to keep out most of the elements, but it's not waterproof. If you're getting dripping inside the car the drains are clogged. Even most aftermarket sunroofs have some kind of drain. Sometimes you can open the sunroof and run a coathanger wire down the drain tubes to break loose the clog. Just be careful that you don't push too hard and damage the drain tubes because they're a bitch to run back down through the frame of the car.

Erik P.
Official 2GNT thread Hijacker
Some say that he's driven over more Covenant than he's shot, and that his grenades aren't where you'd expect them to be...
All we know is, He's not The Stig... But he is The Stig's Spartan cousin!