Whistling sound

[fireftr]

My '05 Limited 4.6 w/125k makes an intermittent whistling sound. Seems to be coming from the dash area. Changing the vent settings (auto, defr, vent), blower speed or temp doesn't have any effect, nor does turning it off. Most noticeable at highway speeds, although I've heard it in city traffic too. Vent system seems to work properly. Happens every so often, and starts and stops when it does. Any ideas?

 

[Number4]

You'll get a lot of responses telling you things you can replace that will fix this. None will. Someone came up with a funny name for it at one point, but it escapes me.
I'm just saying be careful what you replace in trying to solve the issue. $$$
On the other hand, a known fix would be nice. Anyone?

Update - This in only an issue on the 4.6l engines

 

[esclamada]

probably a leak in the vacuum hose. It's very small that it doesn't affect the operation of your vents. I'd wait until it becomes large enough to pinpoint where.



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[ponkotsu]

Whistling sounds are usually vacuum leaks. Maybe try disconnecting the vacuum feed that goes to the dash and see if the noise goes away. If not vacuum or blower related, then maybe it's just an air leak under there. That would certainly correlate to highway speeds.