2001 Tahoe water noise

[Grumpy Joe]

I bought a Hoe from Anaheim Police at an auction. There is a noise behind the dash that sounds like water splashing around. As I accelerate I hear it running backwards and if I stop hard enough I hear it running forward. My thought is the vent duct under the outside grill is not draining. Does anyone else have an idea what it may be before I start destroying plastic parts?

BTW good to be back to a Chevy again after so long.

 

[Grumpy Joe]

WOW no one has pulled apart the dash for a water issue? It is kinda calming, sounds like a water tube on a Relaxing Music CD. Anyone know where the drain tubes come out for the AC/Heat and the cowl hood intake?