Outside air gate

[gary2232]

I am getting truck ready to paint. I removed the cowl to clean and so I could paint the area under it. I was cleaning (Lots and Lots of leaves) and I noticed that there is a diverter flap located on passenger side to let outside air in to cab?? It looks to me that it is open to weather. If I wash that gutter area just under cowl will all that water flow inside my cab?? It looks like rain water will drain in there also. Is this something I should block when I wash that area???