Water leak passenger side

[Ol' Blue]

1996 GMC C1500 5.7 AT
Having a water leak after a good rain from the bottom of the blower hsg. Pulled the blower motor, put garden hose on roof of cab and ran water down the windshield. Water collected in bottom of blower hsg. Pulled off the cowl grill looking for some sort of drain that may be clogged. Could not find one. Any ideas how water is getting in ?

[RayInAlaska]

Originally Posted by Ol' Blue

1996 GMC C1500 5.7 AT
Having a water leak after a good rain from the bottom of the blower hsg. Pulled the blower motor, put garden hose on roof of cab and ran water down the windshield. Water collected in bottom of blower hsg. Pulled off the cowl grill looking for some sort of drain that may be clogged. Could not find one. Any ideas how water is getting in ?

I had a similar problem on my 1988 1500 step-side, and this is what I found after much looking:

I removed the small grill in front of the windshield (between the windshield and the hood's corner at the passenger side). Inside this open area below the grill, I noticed a sort of oval-shaped panel that had a bead of sealant, maybe silicone, all around the panel, but the panel was slightly lifted at one end.

Water was entering into the blower's housing though the spot on the panel that was not properly sealed. I sealed it with black color silicone, let it set completely (a few hours), and then tested it using a garden hose and plenty of water.

The new sealant stopped the leak.

[Cape Codder]

My 98 had the same problem. Water is allowed and air comes into the cowl through the vent panel. The air intake for the heater goes up into this trough and is sealed to it. Water is supposed to go around the raised air intake and drain down the side of the cowl. My truck came from AZ. I see you are from Texas. The foam seal evidently dries out from the heat and decomposes allowing water to leak into the heater. I could feel the seal by reaching up from inside the blower case. You can remove the dash and heater to reseal or do what I did. I cut a piece from an antifreeze jug and put it over the large air intake opening on the passenger side with 3M strip caulk. Air can still enter from the drivers side opening and the water runs out the drivers side now as the cowl it angled down from the center. No more water for over a year now.

[95 S_Trucker]

I had the same problem rayinalaska had on my 96. It would only leak into the blower motor housing. The firewall was dry. I peeled the panel out, cleaned the cab with a scotch brite pad on my die grinder, and siliconed the panel back in.