water leaking inside thru cowl grate

Lots of threads on this. Common sources are the wiper pivots and the windshield gasket. If water from the cowl vent on the outside is coming into the cabin, it means one of two things- either the cowl is packed so full of leaves the water is running over the top of the lips around the cabin vents and into the vent boxes, or it was so full of leaves for so long the lower cowl rusted out and the water is coming through the holes. Because normally, there's a lip that's a couple inches tall around each cabin vent leading into the vent boxes that keeps water from the cowl from running into the vent box.

There's a wiper pivot repair how to here How To Fix Leaking Wiper Pivot Seals