Stock 2000 XJ Sport. I've had it about 2 years.

So. I've had this roaring noise since I had the water pump replaced a few months ago. Like...the DAY I got it back from the shop the noise was there. Pulling off the lot. (Yeah I should have gone back and asked them wtf this new sound was...)

It happens when you first start the jeep and it's in park. It settles down after a minute or two to a hum but it's still abnormal...meaning a noticeable difference from what it sounded like before the water pump.

It becomes a roar between 1500 and 2200 rpms. If I am outside that range it sounds normal again. If I accelerate through the noise, it goes away and if I let off the accelerator it also goes away. Completely.

Could this be the differential? Someone told me that's what it is but why would it do it when I'm in park and only at certain rpms??? And of course it's only when accelerating. The diff is still engaged and turning at 50mph when I'm breaking so why no noise then???? Or do I not understand how a diff works....I've helped take one apart but it was years upon years ago...

To me it sounds like a fan is messed up. It sounds like a fan when I drive it in a tunnel, it sounds like a fan when I go past a solid object with the window down...I mean maybe I'm insane but to me thats what the sound...sounds like. It's also coming more from the passenger side than driver. Sounds like it's slightly to the passenger side of center.

And if it IS the diff...do we agree that replacing the axle with one from a bone yard is easier/cheaper? I feel ok replacing the axle myself. I'd like to do most of the work myself but right now the jeep is the DD and that's why I've let someone else do the water pump and some other stuff....but I want to be sure the diff is the problem.

Feel free to link other threads. I've searched and read a ton but a lot talk about a roaring at certain MPH...mine is RPM not MPH. I've also looked at the "airplane noise" threads which seem to be fan-related...and that's honestly what I was assuming it was until someone mentioned it could be the diff. It very much sounds airplane-take-off-ish. Like...a giant propeller...aka a fan.

Yeaaaahhh....any thoughts welcome. I'm still learning so all help is welcome and greatly appreciated.

 

It is the fan. The mechanical fan is mounted on the passenger side of the engine. I would check with the shop that did the work and see if they changed the fan clutch too while they were changing the pump.

 

While changing the pump, they either screwed up your fan or left it loose. Open your hood and spin the fan clutch with your engine off

 

Question OP, do you hear the noise when the engine is cold.

 

Yep. Its louder then, I think.

 

Thanks!!!

 

Will do.

 

Wanted to rule out engaged fan clutch.

Now, open the hood and make sure the fan clutch and mechanical fan are on tight by pulling and pushing on it forward to back. Honestly I don't think the fan is.loose because it would cause other issues. After you check that, check your belt tension. Try and twist it. Deflect it, see how far down you can push it. After that turn the jeep on and rev the engine by hand at the throttle body. Listen for the noise. Sounds like it may be a bearing.

But did you say when you on your brakes the noise goes away. A differential sound would only be when driving not parked up

 

When he pushes his brakes his engine moves a little. That's why I thought maybe his fan is hitting his shroud and when he pushes his brakes, the engine shifts just enough to make the fan not rub

 

It's not uncommon for a new part to be bad right out of the gate. Could be the water pump they put on. You have to do a big more examining to pinpoint it and see if its really an issue.

 

Will do when I get home and it cools off a smidge. So if I brake OR if I just let off the gas, the noise stops as soon as the RPM's drop. It's instant. And the MPH doesn't matter, can be going 60 or 30. Once RPM's drop under 1500 noise is gone...and if I really punch it going up a hill and RPMs get over 2200 the noise goes away but I can hear the normal engine rev as it's preparing to shift.

Also as an aside, I've noticed no issue with the engine temp while this has been going on. Not sure if that matters but anything with a fan and the cooling I try to watch the temp gauge and have seen no change.

 

Also I don't deny that there very well could be a bad bearing in the diff or something...but I'm just saying that this main (godawful) roaring sound that I can't talk over when driving....is probably not the diff and the person who told me that is no longer trustworthy.

 

This is what I'm trying to pinpoint. Either they set the belt to tight and another bearing is going out on another pulley or the bearing on the water pump is no good and yes it may work but its wearing down.

 

This is why I told him to make sure there's no wobble in the fan with engine off. To rule that out too

 

Fan moves smoothly with no back and forth play. Here's a link to a video of the belt. The cover...seems loose to me. I tightened it as much as I could...but it's still got some play in it. Should it? And should the hose run between the fan cover and the frame or on top of the cover? It was stuck down between the cover and the frame...or does it not matter. I'm just trying to see if maybe there's a vibration there I can reduce.


And here's the engine...it sounds different in person than on this audio when I rev it. Also this was after I tightened the cover...this noise isn't near as bad as the one I get while driving.

And...in the video I hear a knocking sound that is giving me a mild panic attack so that's super. You can't hear the knocking much, standing beside it....just the roar.


The roar is the worst first thing in the morning...might try to take another video tomorrow morning when it's cold-cold.

Also..."he/him" is actually a she/her. Hence the girly hands pushing on the belt.