leaky 2003 Avalange

Tell him to look into the inside cab filters...HVAC there are 2 of them under the Passenger sire Dash I've Heard of some people having the same Problem to find out the filter where it seals is leaking...also look outside with the Hood Raised on the cowl vent maybe Some kind of silicon well fix him up if he or you can't not seem to find the source where its Leaking ...get the Garden hose and under very look pressure hit the outside cowl vent area that should help you find the area good luck either way