My '01 developed a knock. Shocking, I know...

4.0, auto, about 154k miles on it. I believe I am the third (maybe even fourth?) owner, so who knows what kind of shoddy maintenance was done to it prior to me buying it a few years ago. It recently developed a knock which sounds like it's coming from the oil pan area. There's also a growling noise when accelerating from a stop or near stop, but it goes away quickly. The knock seems to go away at speed as well, but I can't tell for sure...


Based on everything I've read here and other forums (I did some exhaustive searching!), I know the likely culprits are piston skirt slap or torque converter bolts. So, I've included a video I recorded today which hopefully is clear enough audio wise for someone here to say, "It's XYZ!"

I realize you folks get this a lot, so I apologize. I'm just trying to nail down what this is so I know how to attack it.

 

Definitely not piston slap. Piston slap is way louder and goes away when the engine reaches operating temperature. Could be a cracked flexplate or a loose rocker arm bolt. I would pop off the inspection cover and see if you can hear it clearly from the flexplate, or maybe even see a crack. Then pop off the valve cover and make sure everything is in working order.

 

Definitely sounds like the flex plat

 

I’ll definitely check the flex plate out, though from what I’m reading that seems worse than loose bolts on the torque converter....ugh...

Thanks for the replies! This place is a great resource!

 

My vote is for a cracked piston skirt. Sounds like mine did shortly before it shot pieces of piston down through the oil pan. If you don't find anything on the flex plate you might want to pop the oil pan off and have a look before the piston shatters. There are u tube videos that show you what to look for. One even showed how to replace the offending piston without pulling the engine. Of course this was a "insert your favorite adjective" fix.
just my .02
Hapdad

 

My Jeep made that sound for a while. Couldn't pin down what the noise was so I decided to live with it. Something went wrong internally and I had to get a new motor as it suddenly started making an extremely loud rattle-like noise. Dropped the pan and couldn't find anything, towed it to the mechanic and he couldn't find anything wrong either. I know this doesn't add much to the thread but I feel like I should say something just so you know it's a possibility.

 

Woohoo! Loose bolts were the winner! Thank the Lord. I still intend to rebuild the engine at some point, but now instead of doing an emergency repair I can save my pennies to do a stroker.

Of course, now my damn brake lights are out. Third light still works, checked the fuse and it’s good. Cleaned my ground contacts under the hood. Not sure if installing the K suspension headlight harness caused it or not. I’ll check that junction in the rear cargo area first and test voltage at the bulb, then work my way back from there. Ugh.

But hey, at least it ain’t spitting out broken skirt! (yet)

 

Very common and first thing to check. Glad you found it.