I've had this whistling noise for awhile now and it's driving me nuts. It's not the intake gasket as it passed all the tests. Bolts are snug and tight. I replaced the wp, psp, alternator and idler as they are original and winter is coming. I thought for sure it was just the alternator since its was making noises. I've narrowed it down to the front of the valve cover. My stethoscope seems to be more pronounced there. You can only hear it at idle and engine drowns it out while driving ideas? Here is a quick video
Thanks

 

Hard to discern the noise in video.. So noise was present before the wp, psp, alternator and idler pulley change? Are you sure rear bolts (more likely on drivers side) on valve cover are properly snug? Thats where my whistle was coming from..

 

Yeah that's the first thing I checked. And the noise could have been there before as the alternator probably over rode the sound I'm hearing now. What's odd is its quiet when I run it with the belt off so it would lead me to believe it's something pulley related. But when I use the mechanics stethoscope over everything, I just hear normal operating sounds from everything. The moment I probe the front part of the valve cover where the sticker is, the sound is right there. No clue, I'm stumped.

 

Ok, I'd imagine you checked/torqued all valve cover bolts to spec.. What about intake manifold bolts? All gaskets good?

 

Does the whistle go away when gas is applied? I had the same issue with my 00 cherokee. I would say tighten the intake manifold bolts.But be they need to be re tightened in a certain sequence aswell and certain torque settings.

 

Does it do it when cold, or just at temp?

 

Remove the deer whistles from your grill.

 

Barely on a cold start in in the morning, then it will start when it is warmed up, then continue on through out the day. Yes all intake/manifold bolts are good. When gas is applied, the whistle is at a minimum, but I think its just engine drowning it out.

 

Starting to get to far away from the point where stethoscope has it, but harmonic balancer good? I wonder if the noise could reverb to a point farther away? I really don't have much in the way of facts when it comes to how a noise would work within the engine, but this doesn't sound right to me.. IDK, just spitballin..

 

Yeah I was thinking the same thing about noise reverb. The harmonic balancer was off a couple years ago to replace the front seal and was good then and appears so now. While under the Jeep, I can barely hear it, it's just more pronounced right at the front valve cover. Just stumped, Iv'e done so much searching it's ridiculous. I found a video on youtube with a guy that had the same sound and he never updated or responds to messages.

 

Run it with valve cover off yet?

 

Not yet, that's the next plan, I'll update when I do that. Thanks for your input so far.

 

You're welcome.. Haha, just an opportunity to retighten all those bolts.. Again… I hope you find the source. I'm pretty curious to know the answer myself! Good luck.