water leaking inside thru cowl grate

I made a "U" piece out of unglued 1" PVC pipe that I duct taped to the end of my shop vac and I reached in thru the two under-dash vents (non-AC car). Then I vacuumed full circle around the cowl opening to get out all of the pine needles that collected there. If you also have rust holes, then this will show up inside the car on the flooring. First guess is usually the wiper pivot shaft seals though. But if you can see junk inside the cowl, you should definitely vacuum it out too.