noise I cannot figure out

[Donald]

My Jeep makes a sound when the temp is cold and engine is cold that sounds like a piano tuning fork. It eventually goes away as the engine warms up.

 

[turtlevette]

accessory bearing (alt, wp, ps pump)or idler bearing going out?

get yourself a mechanic's stethoscope or stick a piece of small hose in your ear.

find it.

 

[tomcat27]

My jeep 4.0 used to make a funny whistling noise.. It was the egr valve...

 

[Donald]

It does not sound like a bearing noise. More like an audio noise. Feedback when a microphone is too close to speaker.

 

[jeepman3071]

It is hard to diagnose a noise without actually hearing it. At this point we are just guessing. I'd say pull the serpentine belt and run the engine briefly when cold to see if the noise is accessory related. The belt is pretty easy to remove on a 4.0 engine.

If you can get a youtube video of the noise that would help too.

 

[Rand]

I'm not familiar with the jeep engines.. if it was a ford 4.6 I'd say IAC.

since its not best way is to record it

(for reference FORD IAC VALVE NOISE)

https://www.youtube.com/watch?v=JpVf-NzCuDs