Edit: I now know that dent in the exhaust is factory. My apologies for not knowing! Please read through my post and let me know your thoughts, thanks!

Back again for help from the experts. This time I have a picture!



Can't get the picture facing the right way. That's right below the header, next to the oil pan.

Is this the reason my XJ sounds like a diesel on start ups? It only sounds diesel/clattery on start ups. It's been doing this a decent while now, as I posted about a "knock after cold start up" back in November. It only lasts until I've driven a couple hundred feet then it sounds just fine.

I've checked the torque convert bolts, all are tight. I'm running Rotella T6 5w-40 and a Wix 51515 oil filter. Oil level is spot on and looks good. Didn't have any metal shavings when I changed the oil about a month ago. Oil pressure climbs right up to about 45ish on startup, and I average 18.5 mpg (25% city, 75% highway). So I don't think it's something serious, but I'm no expert. Plus I would expect something would have gotten much worse if it was a serious issue, and that it would be a more constant noise.

Is this just normal 4.0 sounds, and I'm being paranoid as usual? Again it's been happening a while now. I've heard possibly oil filter, but again, been hearing it a while.

97' Sport, 4.0L, AW4, NP231, 72k

 

That is a factory dent. It's for diff clearance. It won't make your rig run bad.

 

Seriously? Wow, I feel like a moron now. My apologies.

I wish I had an idea of why it sounds like a diesel on start up.

 

You're not the first to think they had a defective pipe. Now you know.

 

/thread

 

Another theory is that the dent is there restrict the flow and make it hotter for the catalytic converter.

 

The lifters in the xj are known to tick maybe thats what your hearing?

 

Thanks Andrew, I've thought about that too. Maybe piston slap? But I thought that was more in cold weather. It honest rides pretty damn nice for the most part. Some days better than others, but I think that's normal.

 

Cracked exhaust manifold that is noisy at start then warms up and quiets down?

 

All the 4.0's are noisy on startup that I ever heard, but none sound like any of my diesels have 4 of those one a 6 banger Cummins.

 

It's not a theory..............

 

I know, but you know how people get when you start spouting facts.

 

Yes. Sorry. I had a momentary lapse of sanity....

 

Lol! Know the feeling.

Appreciate it guys. Considering the length of time this has been going on, I'm assuming it's not serious.. Will taking the belt off and starting it up for a few second tell me anything? I've come across this while doing my searches. Just not sure exactly what it will tell me.

 

I don't think so based on your info. It might tell you if something connected to the belt was making the noise. I've always thought my Cherokee sounded a little bus like sometimes.