So recently we got some snow and cold weather in DFW and throughout that time my XJ (2000) sat parked. I did warm it up a couple times to make sure everything was alright. The second time I did though it gave a loud chirping noise from the engine bay. It was about 10 degrees outside when it first happened. I assumed as it was cold it was just one of the pulleys frozen up or cold and needed to warm up. Now we are back to regular weather, yesterday when I was leaving work I started up the Jeep and it started the same chirping noise. It’s loud like a squealing pig but not consistent. It chirps loud (consistent with belt revolutions) then it can quiet down and chirp just twice and it does this until the xj is warm. I tried turning the A/C on and off and it did not help. I haven’t had time to pull it in the garage and mess around with any of the pulleys. It may be something else but I wanted to see if y’all have any insight on this before I start playing around with it. Could it be something else? If it is a pulley, where should I start? Can i grease anything to help or try to diagnose? I watched a few videos and read through some forums but haven’t got any clear help. Thanks in advance!

 

First thing to check is the serpentine belt. The belt on the 4.0 needs to be pretty darn tight to stay quiet. If it's an old belt, just replace it with a quality belt, you get what you pay for with belts. The old Goodyear Gatorback (now Continental Elite) is a good choice.

While the belt is off, start the engine for a few moments and see if the noise is gone and if it is, that confirms the culprit it is one of the components along the serpentine belt route. While belt itself is high on the list, any component along that route can be involved such as idler pulley, alternator, air conditioner compressor, etc. Turn each component by hand when the belt is off, should all turn very smoothly with zero resistance.

Good luck, keep us updated!

 

With the engine running, hvac controls off the 2 defrost selections and the belt squeeking spray some plain water on the belt. What happens?

 

I agree all the above is a good start... also just tossing this on the table... if you're belt is in good condition, recheck the tensioner.

Also... just to keep the playing field open here... unless we know it definitely IS the belt as the cause.... when it's cold out... lots of things can rub and squeak as the low temps cause materials to contract slightly.

 

I had a chirp chirp chirp the entire time the WJ engine (4.0) was running.

I replaced the idler pulley. Still chirping.
I replaced the tensioner. Still chirping.
I replaced the water pump. Still chirping (grrr).
Then I found out that sometimes the harmonic balancer wears out and gets out of alignment with the belt.

My balancer was only misaligned a tiny but, just enough to make the belt sqeal. Eventually it would have shifted enough to throw the belt off. Or even completely come apart. Neither scenario would be good.

Here's what my bad one (right) looks like compared to the new one (left). Hope these pics help someone before they replace parts that are unnecessary.


This amount of offset of the harmonic balancer is enough to cause chirping or squealing.


The slight offset on the inside of the rubber ring in the right pic and the cracks in that rubber ring are indications it is time for renewal.
Hope this helps!