Help with unusual KJ noises - videos

[2002_KJ]

Hello,

I have these two distinct noises coming from the rear of my 2002 KJ 3.7L V6 automatic.

The first is a continuous hissing noise that seems to be coming from the rear axle/differential area. Some research lead me to believe that perhaps it has to do with vacuum tubes or fuel vapor tubes but I thought I’d make a quick video and see if anyone can help confirm.

The second noise also seems to be coming from the rear undercarriage area and its a continuous rhythmic thumping. I was thinking maybe something to do with the exhaust?

I realize I just need to get under there and poke around but again I figured if I made a video and asked here first maybe I’d have something to go on, thanks!

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[LibertyTC]

I only see images no video, try youtube..
Just to be sure, Is the rear diff a hissing noise while parked ?
If so it may be best to have it tested by a shop that has a smoke machine.
Look forward to 2nd video, thumping noise as well.

 

[2002_KJ]

I only see images no video, try youtube..
Just to be sure, Is the rear diff a hissing noise while parked ?
If so it may be best to have it tested by a shop that has a smoke machine.
Look forward to 2nd video, thumping noise as well.

Sorry, I tried using Imgur which is terrible...I edited the post and uploaded them to Vimeo, hopefully that works better.

Yes the hissing noise is there while in park.

 

[2002_KJ]

Resolved.

In case it might help someone, the hissing noise did come from the cracks in the vacuum tube and fuel vapor tube of the rear fuel lines, near the differential. Replaced and no more noise.

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[LibertyTC]

Good Job, This may definitely help others.

 

[2002_KJ]

Good Job, This may definitely help others.

Thanks. I wonder if there was any effect on engine performance or fuel efficiency or emissions with all that hissing

 

[LibertyTC]

Pretty sure it would have effected Jeep is some way, how was it when driving?
Did an engine light or code ever appear ?

 

[2002_KJ]

Pretty sure it would have effected Jeep is some way, how was it when driving?
Did an engine light or code ever appear ?

I couldn't really tell much of a difference before and after, feeling-wise, other than it not sounding like a locomotive anymore with all that hissing and thumping. Hard to tell really...maybe a little less sluggish? Like the tires had been filled up with air if that makes sense.

Engine light never came on though, which I kinda would have expected. I'll see if the MPG average goes up after a while...