Re: 2006 expedition
It could be a dash panel or even worse, a loose ventilation tube which can be hard to get at. Take all loose items out of the glovebox and on the floor as well as in the center console. It's best to take someone along with you to help pinpoint the noise unless of course it's noticeable at idle.
'11 Ram Quad Cab 4x4 SXT 5.7L HEMI (stock); 48,500m
'06 Pontiac G6 GT 3.5L 220hp; 64,000m
'12 Chrysler 200 Limited 3.6L 283hp; 28,000m
'99 Taurus 3.0L 2V Vulcan 145hp; 154,300m - Traded
Amsoil in all vehicles!