Hey everyone, I just bought my first XJ about a month ago, learning a lot. It's a 2001 XJ. One problem I'm having though is that it makes this extremely loud hissing noise for about 5 seconds whenever I start it up for the first time that day. It only does this when it is completely 100% cold (so usually one time in the morning). It does not do it any other time throughout the day. I had someone else start it up one time while I was under it to look for the source. I did not see anything out of the ordinary, but it seriously did sound like it was coming right from the oil pan. I know that does not make any sense. The link here will show you a video of my Jeep making this noise.

https://photos.app.goo.gl/cBF73Vp8KHiS3CQW6

Even though I don't think any of this has to do with it, below are a couple details about my XJ that might help
- 2001 with 140K miles
- (standard) 4.0L I6 engine
- Transmission: AW4, four speed automatic, model # 30-43LE
- Since I've had in, in the last 4 weeks, I done the following maintenance: new fuel injectors, new oil pressure gauge sensor, new fuel line (replaced rusty line running from tank to charcoal canister), new oil and filter (10W-30), new air filter, and new spark plugs (copper, NGK)

Any help would be greatly appreciated!

 

Starter hanging up? Sticking and not releasing from the flywheel as quickly as it should?

What's the condition of your serpentine belt?

It sounds very mechanical on the video vs a hissing.

 

Serpentine belt looks fine. I have not checked the starter. I don't know much about starters or flywheels. What should I look for?

 

2 approaches for this. Pull the inspection cover OR pull the starter. Either route look at the condition of the flywheel teeth, if you pull the starter then inspect for the looks of excessive wear to the starter teeth as well. If its starter related the wear will stand out because things are gonna be shinny with excess metal dust and maybe even flakes.

 

If someone forced me to guess, my guess would be power steering.
Do you get any trace of the noise when you turn the steering lock to lock?

Does it sound like it's coming from the power steering pump when you start it? Need 2 people.


Keep in mind it's close to impossible to diagnose noises on the internet. I'm basing the steering guess on the sound AND the fact that it's one time after an overnight soak.
One thing to try would be to take the belt off before you start it in the morning and see if the noise is gone. That would narrow things down.

 

Update, it is definitely the starter. I had someone start it up while I was under there. I've got a new starter on the way so should be good to go. Thanks y'all for the help.

 

Starter making the hissing sound-
now I'm curious!

 

More of a zzz than an sssssssss.

 

Vs a Werrrrrrr and a clunkerk hkkkkk hkkkk?

 

New update, i replaced the starter and it's still doing the same thing...?

I'm not a mechanic by any means, but when I posted about this here as well as on Facebook, the first thing I got from 2 sources was the starter. When I was looking under there as my friend started it, the noise was definitely coming from the starter.

Idk. Maybe it's something to do with the gears the starter connects to??

 

not gonna lie that sounds like the belt squealing. take the belt off and try and start it. if it doesnt then go from there.

 

engine noise location 101

next step, a mechanics stethoscope ($10) or any long solid rod (large screwdriver will do)

its mesmerizing hearing all the mechanical bits whirring

OHS warning, dont put you head too close to moving parts (although head butting a non moving piece of steel is not nice either)

 

 

I just knéw it lol
it should be in your sig

 

For anyone that comes back to this thread or was wondering, in the end, it actually was just the serpentine belt. Took it out, cleaned it, good to go. Thanks all.