Ok, well, I just bought this 99 XJ a week ago and...it's got some bizarre intermittent noise I can't figure out. While driving, it makes what kinda sounds like a wind whistle but is extremely loud. Here's what I've been able to determine so far: I does not do it at idle, I have to be moving, usually 30+mph, seems to happen mostly when maintaining speed or decel, is not speed sensative, does not get louder or quieter if I go faster or slow down. Also, the pitch is always the same, is not realted to engine speed or vehicle speed, is nothing rotational so revving the engine or downshifting or anything like that does not change the pitch. Opening the window does not change anything, a/c on or not changes nothing. Nothing I do changes the pitch of the noise, and when it occurs, is so loud, it hurts your ears and can't have a conversation in the car. I'm pretty sure it's from drivers side. Yes, I checked manifold bolts/nuts, they're all tight. I'm gonna take a wild *** guess and ask...is it possible my brake booster could have a vacuum leak and make some weird noise like this? Or, has anyone else reported anything like this? I couldn't find much in a search.

 

Sounds like the wheel bearing hub. On these XJs, it's complete unit of the bearing and hub. I used Timken when replacing them on my '99 and my '95 YJ. Rockauto is a good place to start (http://www.rockauto.com/en/catalog/j...+assembly,1636). Or Amazon ( ).

Getting an original one out can be difficult as the hub will fuse to the steering knuckle. You can search for that problem. It's a good first project for an XJ.

 

I'm not convinced its a hub or bearing noise, isn't constant, doesn't change pitch or intensity with vehicle speed.

 

If it really does not respond to RPM changes (motor or wheels). 2 things that would come to mind would be the electric fan (bearings, clearance, etc), or perhaps the cooling system. Even something like the brake booster vacuum would change a little as RPMs went up and down and the vacuum levels changed.

 

 

Well, I found a cracked line from the PCV valve to the manifold, replaced the line and pcv valve and.....no difference. Noise is still there. I also went thru two cans of carb cleaner looking for vacuum leaks, sprayed all the vacuum lines, brake booster, the throttle body, intake manifold, everything I could think of or find that had vacuum going to/from it and nothing, no vac leaks as far as I can tell.
I have no idea what to do next.

 

we have a loud pitch noise in the cabin but not constant only when starting a cold start, i believe its the blower motor.

marc

 

you could try fiddeling around with the vent selector put it in between the settings see if that changes the noise

 

That damn noise was driving me nuts, I would have bet my last dollar it was from the firewall/engine area. But, finally found it, was the light bar above the windshield making noise above 40 mph. Wind had to hit it just right, and it'd start whistling !! Light bar is GONE now and so is the noise .

 

I bet it looks much better now as well haha

 

lol, at least you solved it!

edit: perhaps mount it more backwards? im sure it will change the pitch somehow

 

Does that light bar have cooling fins running across the length of it on the back? Someone here had one that was whistling like yours, so he ran a bead of silicon from top to bottom across the cooling fins on each side to disrupt the resonance. The whistle stopped.

 

Yes. mine had many, very deep cooling fins running the entire length of the light bar, essentially a huge heat sink. But, the light bar is gone. I removed it entirely and sold it on FaceBook. Previous owner did a lousy job of installing it, scratched the hell out of the roof and rain gutters. Light bar didn't work, was poorly spliced in three places, and I found the relay they installed had melted as well. I'm happy it's gone and the noise is gone as well. I