Whirling/Chirping noise from engine bay

[Fred85]

My Jeep has developed a sort of whirling/chirping noise coming from the engine (it actually sounds like a bunch of crickets, which is the best way to describe it). It's directly related to throttle input and doesn't make the noise when revved in park/neutral, which makes it hard to diagnose.

I feel like something is going to break soon, so any ideas of what could be creating the noise would be much appreciated!

4.0, AW4, NP231

 

[lazyxj]

Try removing the serpentine belt and then checking that everything the belt drives turns freely, with smooth turning, not chunky feeling, bearings.
While the belt is off, fire the motor and listen, rev it a couple times. The water pump will not be rotating so only do this for a short period
You will be amazed at how different the engine sounds when the accessories are not spinning.
Check the condition of the belt and reinstall it or a new one, using a belt tension gauge.
Krikit Serpentine Belt Tension Gauge
http://www.rockauto.com/catalog/moreinfo.php?pk=101692
Serpentine belts need to be tighter than what most assume.

 

[Flyfisher]

Seriously, no noise in park/neutral? Then must be related to engine torque...twisting under load. Look for wear engine/transmission mounts making something rub. I originally thought serpentine belt, but that doesn't change with respect to being in or out of gear.

 

[iwannadie]

Seriously, no noise in park/neutral? Then must be related to engine torque...twisting under load. Look for wear engine/transmission mounts making something rub. I originally thought serpentine belt, but that doesn't change with respect to being in or out of gear.

I've had a loose belt that caused that type of sound and wouldn't do it when I fired up the XJ, it would however do it when I put it in gear to back out of the garage. Maybe more strain by being in gear.

 

[98NWCherokee]

Just resolved a chirp underhood in my 98. It was a bushing in the distributor that was failing. It was an easy replacement at about $120 for a new reman unit. No chirp in the 200 miles since.

 

[Fred85]

Just an update for anyone searching: it was the CV joint on my rear driveshaft. I sprayed it down with WD-40 and the noise stopped, so it is apparently a lube issue

 

[mfascuba]

I had a chirp from the idler pulley on the serpentine belt. Mine is a 97, there is a tension adjustment and then there is a fastener on the pulley that needs to be tightened as well to lock in the tensioner adjustment. The second fastener is not intuitive.

 

[Ben824]

Just an update for anyone searching: it was the CV joint on my rear driveshaft. I sprayed it down with WD-40 and the noise stopped, so it is apparently a lube issue

WD-40 is not an adequate lube for that joint. All you did was put a band-aid on it. You need to remove the driveshaft and run it by a local shop and have them shoot some grease in it with a special grease tip. It is not a standard grease fitting since it is in such a tight location. You can purchase the tip and keep it on hand to do yourself if you choose. Shouldn't cost you more than $10 at the very most. If your joint does not have a grease fitting, then REPLACE THE JOINT! There are serviceable joints with grease fittings and non-serviceable joints without grease fittings. If you do not replace the worn joint then it WILL seize and WILL lock up and you will find yourself with a broken driveshaft and cracked transfercase housing.

 

[Fred85]

Trust me, i know! I was just happy to find the damn problem...sounded like a game of angry birds underneath my jeep

 

[Ben824]

Trust me, i know! I was just happy to find the damn problem...sounded like a game of angry birds underneath my jeep

Ok good you never know sometimes with some people on these public internet forums. If you google "Jeep angry sparrow" you will find lots of info on this. I have had to deal with this 3 times now. First replaced the original factory one with an aftermarket one, which went bad and I had to replace it again after 2 years. I replaced it again with a different brand and it was good for about a year and a half before it started making the sound again. I had a shop shoot some grease in it and it has stayed quiet up until today where I could just barely hear it with the music off and off the throttle coasting. I'll pull it and have a shop shoot some more grease and away I go!

 

[Fred85]

I assume you mean shoot grease into the CV ball, correct?

 

[Ben824]

I assume you mean shoot grease into the CV ball, correct?

Yes I was referring to the Ball Centering kit in the Double Cardan joint at the transfercase end. The "fitting" looks like someone started to drill into it but stopped before it started making the hole. Someone had to point it out to me since I had never seen one like that before.