2000 XJ - Knock knock?

[Herzog]

I had to pick up my kid and his XJ on the trailer today, it developed this knock... I'm not super engine savvy but it sounds to me like a possible rod knock or piston slap, especially comparing to other videos with the same diagnosis. My hunch is the piston skirts left the chat.

I'll be dropping the pan soon to verify, but regardless sounds like it has problems. So, question is, bottom end rebuild or just find another engine to swap in? Almost 300k miles...

Note - the noise isn't coming from the top end, hard to tell in the video but the valve train up top sounds good.

 

[STAG]

Slap a Cummins sticker on the back window and run it!

Kidding, but I have heard of 4.0 people successfully throwing in new crank/rod bearings while the engine is still in the unibody rails, not even pulling the block.

 

[Herzog]

Kidding, but I have heard of 4.0 people successfully throwing in new crank/rod bearings while the engine is still in the unibody rails, not even pulling the block.

Yea I've been on a youtube binge looking at similar situations trying to decide what to do. I think it will be a pretty good opportunity for him to learn a lot about his engine either way. Seems like not too big of a deal to rebuild in the bay there.

 

[bryson]

Automatic? Could be a cracked flexplate or something too...

 

[STAG]

Obviously

 

[Mouse]

Hard to tell over the internet. I had an XJ once that sounded similar and we assumed it was a connecting rod bearing. Had somewhere around 300K on the engine. We decided to pull the engine and found a flex plate bolt had backed out and was hitting the block (slightly). tightened it up and it sounded like a normal 4.0 again

 

[Hickey]

Automatic? Could be a cracked flexplate or something too...

That reminds me. I bought a 94 XJ many years ago that had a pretty bad knock. Sounded like a rod knock, but it was several missing bolts on the bellhousing. Replaced some bolts and it ran awesome and smooth. I wish my YJ had that kind of power.

 

[N-Smooth]

I came here to mention the loose flexplate bolts.

 

[Herzog]

Cool, I’ll pull the inspection plate off and check those bolts. That would be awesome if that’s all it was. It does sound lower and closer to the transmission.

 

[Herzog]

Automatic? Could be a cracked flexplate or something too...

Hard to tell over the internet. I had an XJ once that sounded similar and we assumed it was a connecting rod bearing. Had somewhere around 300K on the engine. We decided to pull the engine and found a flex plate bolt had backed out and was hitting the block (slightly). tightened it up and it sounded like a normal 4.0 again

That reminds me. I bought a 94 XJ many years ago that had a pretty bad knock. Sounded like a rod knock, but it was several missing bolts on the bellhousing. Replaced some bolts and it ran awesome and smooth. I wish my YJ had that kind of power.

I came here to mention the loose flexplate bolts.

Well I'll be damned...

 

[Hickey]

Well I'll be damned...

View attachment 172733

Wanna know what really bugs me? Driving my severely underpowered 4.0 YJ around, while remembering how my 1992 XJ with a 4.0 had WAY more get up and go.

 

[TRD270]

Wanna know what really bugs me? Driving my severely underpowered 4.0 YJ around, while remembering how my 1992 XJ with a 4.0 had WAY more get up and go.

92 was the first year of the “H.O.” 4.0 right? Is it that big of a difference? I’ve only owned pre H.O. 4.0… and horrible emission era 4.2

 

[jeeper]

I love an easy fix, and I love that so many guys here knew about it. RME is the cats meow.

 

[Herzog]

I love an easy fix, and I love that so many guys here knew about it. RME is the cats meow.

I was prepping for the worst. Love a good sigh of relief! Now on to the next project, ahead of schedule! 😂

 

[jeeper]

I was prepping for the worst. Love a good sigh of relief! Now on to the next project, ahead of schedule! 😂

My brother does national park tours. He was doing the river crossing in capital reef last night and it got a little splashy. He sucked water through his motor. I ran a truck down to him last night and I’m bringing the suburban home this morning. Now that it’s daylight, I can see a hole in the side of his engine block. He definitely got the worst! 😬😕

 

[Kevin B.]

My brother does national park tours. He was doing the river crossing in capital reef last night and it got a little splashy. He sucked water through his motor. I ran a truck down to him last night and I’m bringing the suburban home this morning. Now that it’s daylight, I can see a hole in the side of his engine block. He definitely got the worst! 😬😕

View attachment 172738

He did that crossing the Fremont?

 

[jeeper]

He did that crossing the Fremont?

Yeah. Crazy, eh?

 

[jeeper]

This is my brothers suburban

.

 

[Tonkaman]

This is my brothers suburban

View attachment 172819View attachment 172820View attachment 172821.

So what happened? Please don’t tell me he had clients with him