To correct my passenger rear foot area "pond" that accumulates during a rainstorm, I tried to unplug my sunroof drains and also the drains under the hood latches (larrybible). What I did was slowly pour water thru the drains via a funnel at the entry points.
Conclusion: The two front drains on sunroof drain between the the front door and fender. the rear sunroof drains drain behind the trim on the rear doors and then the water will run down the side of the vehicle. The under hood hinge drains, drain at a point about even with the drains but a little under the engine. All the while I was monitoring the rear passenger foot area watching for any sign of water. I never did see any.
At that point I had to go to work. After about 5 minutes of driving I happened to look back and there was a little water in the foot area.
(Hey Larry Delor, I tried to stick a coat hanger up that drain that was even with the rear axle and the hanger would go about 8 inches in and would get hung up. Doan know if it was cuz the drain hose would turn sharply and the hanger wasn't flexible enough or what)
84 500SEL EURO 87K
85 300D 267K (and still goin' strong)