Chevrolet Repair Questions? Ask a Chevy Mechanic for Answers ASAP
It's possible you have a rust hole on the inside of the cowl. To inspect it you'll need to remove the wiper arms and screws holding the cowl vent and the vent. It's not uncommon for debris to build up in there and hold water causing it to rust through.
Let me open this back up to see if any other experts have any thoughts. Someone should be with you shortly.