2000 Chevrolet S-10 • 160,000 miles

I have a 2000 Chevy S10 Pickup and my heater started making a Humming noise. If I Unplug the Vacuum Hose from the Nipple that goes in the Fender Wall, it quits humming but sucks a lot of air through the T. Does anybody have any ideas on why this does this or what the problem could be?
Dirt Reaper
June 12, 2013.

If I recall, the breather goes into the fender on a 2000. If that noise stops when you remove it from the fender, there must be a blockage either in the hose or the fender itself. Make sure no leaves or other things are blocking things.