01 jeep xj, inline 6, 4.0, aw4, d30 d35.

ok little history, bought this jeep last sept. since I had it I had to replace the head(0331 crack but pretty sure I caught it fast enough.) new plugs, radiator, belt, idler pully, thermostat water pump.

In my care its never overheated. always managed great oil pressure and still does.

I run Mobile 1 full sythentic 10-30 high milage with a mobile 1 filter. Also to note, I have taken the bolts out of the flywheel/torque converter and red loctited each once and re torque them. so unless its cracked around the shaft then thats not the issue.

fast forward to now. I have this knocking, tic...hard for me to narrow it down.

this really has only happened for the last 3 months or so noticably. but what makes me wonder if I did infact catch the cracked head fast enough. either way here is a video.

this is a coldish start up, and it seems to me, the knock or "noise stays pretty consistant. weather cold or warm, but it most notiable during idle. Also, for sake of trying I drained a quart of oil and put a quart of marvel just to see if that does any "magical wonders"... last resort really.

 

btw the check engine light is on for an emission leak..

 

have you cut open an oil filter yet?

 

not sure what the point of that would be. I am doubtfully there would be any visible metal debris in it. I didnt notice any debris in the oil either. I drained a quart off friday to add a quart of marvel mystery oil.. When I chane the oil I supposed I will check. figured Id drive the jeep a few more days with the marvel in it. Then I will change the oil with rotella T6 5-40, and a wix filter and see if that changes anything... If not I think I am going to see about an exhaust leak. see if the manifold is cracked or something. pretty much going to cover everything I can before I buy and rebuild a motor..lol Which if I do I may stroke..lol

 

Sounds nearly identical to my 2.5L that's been diagnosed as piston slap on here. Have you tried unplugging injectors one by one to see if it goes away or quiets down? Mine is #4 making noise. Without it firing, almost no noise at all, very faint. Can only hear it at and just off idle. Still makes good oil pressure, too.

 

What's the process cutting the oil filter just cut the top off?

 

cut the body anywhere it allows you to remove the pleats and inspect what they caught.

 

Looking in to the filter for metal is not the best way. Most metal will settle to bottom of pan and never be picked up by the pump. Drain oil into a clean pan and filter it through a fine mesh screen....a re-usable coffee filter works great. A little slow so be patient,works best when oil is hot. Use a magnet to find out what you discover,bearing material is non-ferrous so it will not be picked up.

 

Try Rotella 15-40 and see if that helps. Otherwise, it don't think it sounds too bad...more or less normal for an old engine. How many miles?

 

 

well go under the jeep and took a vacuum line and put it in me ear, and started listening. I am hearing the noise the loudest in between the tans and the engine! so hopefully its just the flexplate!

buddy of mine has a lift and trans jack..so yay!!! get to drop that and find out. if its not the flex plate, looks like I will be sourcing a 01 4.0 since from my understanding is older motors wont work with my year. when I find one, I am going to probably build a 4.7 stroker. might even say to hell with it and build the 4.9l stroker...

 

I think you're just looking for an excuse to convince yourself you NEED a stroker... Most other people will drive on...

 

Not really...I honestly dont feel like sinking that kinda coin into a non preforming setup. But if I had to build the motor I will do it right. I have an 81 c10 thats my money pit. So any coin saved goes to that...turbo 5.3 build...frame off restomod. My jeep is just my daily driver... so nope not lookin for excuses. Just hate hearing knocking noises on my vehicles..

 

Almost every 4.0 I've heard has sounded like that. Completely normal. It is piston slap and they all get that when they get older.

I've noticed running Pennzoil Yellow Bottle 10w30 seems to quiet mine down a little from the high moly content in the oil. You might want to try that and see if it helps.

That isn't flex plate noise. The flex plate makes a much louder knock that sounds like rod knock, but will change when shifting into drive and reverse.

 

My 4.0 sounds EXACTLY like that... no worries.. drive on!

Infact.. if it did not make that noise.. I would get scared