Question about 2004 GMC Envoy
It sounds to me like you may a vaccuum line thats either leaking or detatched. What your hearing is the vaccuum controled vent system that determines where the air(a/c or heat) is directed out, at your windshield, dash vents, floor vents. . etc. Unless you smell exhaust, i wouldn't be concerned. Theres small plastic hoses behind the dash. have a person that knows what they're doing to take the dash apart if you can't do it. check these small lines for fit or cracks.
Posted on Jan 23, 2009
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