So I have a high pitched whistling noise that occurs only when the truck is cold ( as in when I first crank it up and start driving after sitting for a while) at and around 2000 rpms. It sounds like a turbo whine.

After the motor warms up, it goes away. Has anybody ever heard of such a thing?

2009 XLT 4.6 3V 6 Speed 4X4

 

Vacuum leak perhaps?

 

I was thinking either that or an exhaust leak. Either way it's going to be hard to figure out since it only happens when the truck I cold, it stops after a minute, and you have to be driving.

 

Check the exhaust gasket between the header pipe and the exhaust. There is a bolted flange with a gasket. If the bolts become loose, the gasket will leak until it warms and swells. It does not take much. Happened to me on '98 4.2 liter. Worth a try anyway.

 

I will check that out when I'm down there. Thanks