I just got a new 2001 xj with just over 125k miles. I did an oil change as soon as I got it with a napa oil filter and Rotella 10w30 oil. I noticed every now and again it had a slight Ticking noise. I checked all the usual causes, flexplate bolts, exhaust, and so on. No dice.

So i just let it go and hoped it would go away. It did not.

I tried some atf fluid in the oil before my latest oil change and it seemed to help, but not much. So I changed the oil to rotella T5 10w30 and...

It has a mind of its own, on startup, it is super super quiet, not even valve train noises. 10-15 seconds later and it sounds like I am throwing a rod.

I know it is Ticking/ Knocking once every other revolution (I am good at math), and that it comes and goes. The jeep has no leaks, great oil pressure, and runs at 212 F in all temperatures.

I was told that it may be a collapsed lifter, but Wouldn't that stay the same and not go away?
Sorry for the long post, but I just wanted to see if anyone has any ideas.

 

Have a video of it? (Or, can you track down a youtube video that sounds the same?)

 

I just uploaded this, http://www.youtube.com/watch?v=L6BzH...1&feature=plcp

 

To me that sounds to hard of a knock to be valves. Although I could be wrong. It sounds to me like a rod is knocking. When you rev it up does it go faster with the night rpms? You might try changing the oil and subbing a qt with Lucas oil. But it really does sound like a bearing gone bad

 

That was my first thought but, it goes completely away after I rev it past 1500 rpm or so and, it also will completely go away at idle when it wants to.

I also just did an oil change 200 miles ago with synthetic blend Rottella T5 10w-30 and a mopar filter.

If it helps, it is a LEV, and has 3 cats, 4 o2 sensors, and an evap system that would make a prius driver smile.

 

Was it doing this when you bought it, before you changed the oil? I thouhgt Rotella was engineered for diesels.

 

Yes it did it before i changed the oil. And yes Rotella WAS engineered for diesels, but they do make oil for other vehicles. Plus the jeep 4.0 engine loves the additives in the rotella oil.

Just for proof, we have ran rotella dino oil in our 98 for 210k miles and the valves are still silver, shiny, and "gunk" free.

 

My 99s 4.0 had similar symptoms that ended up being #2 Wrist pin egging out #2 piston. I could have sworn it was a rounded cam lobe or collapsed or worn concave lifter, and so did alot of other people, except this one co-worker who said first, right off the bat, "Sounds like a Wrist Pin slappin around in a piston". And, he was right. Cheap fix, if you do it yourself, hopefully yours isnt this bad, but id suggest fixing it before it causes any catastrophic damage.

 

Well there are a few things that are slightly different on your 99 than on my 01, First is the head, if it had a distributor then it had a different head, secondly I am sure the connecting rods and other internal engine components are made from a different plant.

You may be correct, but if the wrist pin were bad, the noise would get worse as I accelerate and/or rev the motor, instead the noise goes away. And sometime the noise does not come back for a whole road trip. I still think it may be a collapsed lifter. we will see.

 

Next time it does it on start-up, shut it off for 20 to 30 seconds and restart it. See what the noise does.

 

I have and it depends on what mood the jeep is in. One day it will be worse, next day it runs like an idling prius.

It does seem to be worse is I push it past 3-4k rpm... It could just be a coincidence?

 

Sounds like the lifters are sticky and hanging up sometimes.

 

If that is the case, Can they be replaced without removing the head? If not, She is going to keep the lifter as-is.

 

No, they cannot. Wanna try something easier if indeed it is the lifters? Drain out a quart of oil and put a quart of Marvel Mystery Oil aka MMO. Been working on both of my Jeeps.

 

Mine is doing the EXACT same thing. I am dropping the oil pan this weekend to poke around and see whats up. I have a feeling it is a rod bearing but I am hoping it is a lifter.