water in heater/blower housing and on floor after carwash

[56napco]

2002 Yukon XL 3/4ton. I've noticed in the past that after running the truck through a carwash and then take a left turn afterwards you can hear water hitting the front heater blower fan and a trail of water will be on the road too. Last night I noticed water dripping onto the passenger floor mat after I ran through the carwash and could hear the water hitting the blower fan.

There is also a rattle in the passenger cowl area when driving. The windshield is original and hasn't been replaced before, still has the GM logo. I haven't had a chance to tear into the truck to investigate much between work and working on the garage itself. Has anyone else had this happen or found anything to point in the right direction?

 

[56napco]

So far I've taken the cowl off and inspected under the windsheild and around the fresh air intake and have found nothing. All seals and covers are in place and intact. I did find the rubber flaps (valves as GM calls them) on the LH and RH ends of the cowl had been siliconed on and the RH valve was ready to fall apart. I think this is the culprit of the rattle I've had in this area. I don't see these holding water in cowl area, enough to run into the fresh air intake for the blower motor during a run through the car wash. Doesn't seem to be an issue in the rain or snow, only after a car wash.

 

[56napco]

I'm not sure I fixed the water leak issue but the rattle is gone. I ended up replacing the Cowl Plenum drain valve 15040083 on the passenger side. I didn't take a picture but if you enter the part number into gmpartsdirect you'll see where it goes. The rubber part of this valve was torn away from the plastic base, unfortunately the driver's side part is discontinued and only the passenger side is available.