I've got a leak !!!
You need to understand how this stuff works. The cowl vent is just a big tub, with raised rings that form "dams" for the vents. There are drain holes on the ends. Also in that mix are the wiper pivots.
So in no particular order, we have
end drains clogged, and built up trash and mud in the bottom of cowl This can allow water to spill over the "dams" and down into the vents
Wiper pivots can leak
And the cowl bottom can be rusted / pinholed through
Somewhere I found some photos of one of these taken apart, for illustration
........And here we go, clicky the link
any tips on cleaning out the cowl?