4.0L whistle. Pulley?

2000 XJ 4.0/AW4/NP231 105k miles.


My 4.0 seems to make a whistling sound while idling. Its louder when cold, but is also there when its hot. I've had three cherokees total, and the other two whistled a little, just not as loud as this one.

One thing I noticed was once on a rainy day I started the jeep up and the belt was wet. The voltage gauge read lower (~12 volts) and the jeep seemed much quieter. I then revved it a little and heard the belt squeak and the fan started spinning faster and I also started hearing the whistle. This leads me to believe it is a pulley related problem. My belt is plenty tight, and it doesn't squeal. Has anyone had any experience with this kind of issue? I notice that if I rev the motor from an idle, the whistle will change pitch around 1000-1200 RPM, and go away when I get up to speed or around 2000 RPM. Any ideas? I'd like to have an idea of something to check before taking it apart since this is my daily commuter vehicle.

Mine would have a high pitched whistle/squeal(not belt squeal) when cold and would go away if I reved a few times. Then the idler bearings grenaded. Doesn't do it any more. Take a look there.

smcdonaldaz said:

Mine would have a high pitched whistle/squeal(not belt squeal) when cold and would go away if I reved a few times. Then the idler bearings grenaded. Doesn't do it any more. Take a look there.

Click to expand...

Ok thanks! Can I get a new pulley or do I have to order a whole new assembly for my 2000? I know the idlers are different depending on the year.