Tea kettle noise?

[Boomerweps]

Our 2001 TJ 4.0L has this intermittent very high pitched noise coming from the engine compartment. Both my wife and the previous owner refer to it as a tea kettle sound. I have trouble hearing it but my wife hears it far easier. Previous owner had one of the pulleys and belt replaced but it's still there. It's a little maddening trying to isolate it. Any suggestions? Earplugs are not an option Of course, it doesn't occur when idling in the driveway, just driving down the road at various speeds.

 

[Flib]

vacum leak

 

[CodaMan]

Well, a vacuum leak would happen more at idle since that's when the most vacuum is produced.

Many things can cause that noise ... from a belt to a pulley all the way to an intake or exhaust manifold leak.

You can try looking for a vacuum leak by squirting water or carb cleaner around all the vacuum lines with the engine running.

If it's a manifold you can try re-torquing all the manifold bolts. Keep in mind that if the manifold has been leaking for some time the gasket may now be broken and retighting may not fix it.