2003 Hyundai Elantra GT with leak from sunroof - how to resolve

I noticed water sloshing on the passenger side floor after a heavy rain, and the carpets became moldy. I wound up cutting out the moldy carpet with a knife (be very careful not to cut any of the wiring). But I could not find the source of the leak.

One day I played with the sunroof, to ensure it was all the way closed. The next day it rained and water started dripping from the sunroof into the interior. So I was sure the sunroof was the issue. I mistakenly assumed the gasket around the glass was bad.

Turns out most sunroofs (on several makes of cars) have built-in drainage tubes that allow any water that gets past the sunroof seal to drain down to the ground. These drain tubes get clogged, and several YouTube videos show snaking these tubes using about 6 feet of plastic string trimmer (weed wacker) line. I tried it several times but could never get the line unclogged (testing by pouring water into the sunroof channel should result in water puddling on the ground).

I finally resolved the issue by unfastening the plastic mud guards within the inner wheel well of the two front wheels. These plastic guards do not have to be fully removed. Just remove the three 10mm screws at the bottom edge behind the tire, as well as one more about 12 " higher up. Then pry out the plastic captive nuts that these four screws went into using a flat blade screwdriver. Finally, there are three more 10 mm machine threaded bolts to remove: The first is about 6" in from the first three screws (at the bottom, but in 6"). The next two hold the bottom of a thin piece of the front fender (located between the back side of the front wheel and the door) and bolt directly upward. Once these 7 10 mm fasteners are removed, you can partially pull away the plastic mud guard in the wheel well, as well as partially pull away the thin section of fender from the bottom of the car. This gives you enough room to finally see the exit point of the front sunroof drain tube. In my case there was a huge amount of dirt -- more than enough to fill a quart size ziploc bag -- that had accumulated inside and had blocked the drainage tube.

By removing the dirt and leaves and then snaking the drain tube from the bottom using string trimmer line I was able to unblock the drain. I snaked all the way to the sunroof, but the clog was near the bottom. Finally, I poured a quart of water into the sunroof channel to verify the water drained well (it did, though it was a little slow at first). This needed to be done on both sides of the car.

I've seen diagrams showing four sunroof drains -- one at each corner of the sunroof. But I was never able to see any rear drains from above, let alone snake them. If I notice any further leak after a rainstorm I may remove the rear wheel well mud guards and look for a drain exit that I can snake from below.