Mine was full of leaves, dirt, holes were almost blocked at both ends.
Black thing comes up with 6 screws and removing one windshield wiper. the
water channel goes down the inside of the panel, and will collect as dirt at
the bottom. Small plastic piece withtwo screws can let you into the area,
between the engine firewall, wheel well, and inside firewall, tight place
lots of crud can get stuck there and rust things out.