2000 XJ - Knock knock?

Herzog

somewhat damaged
Admin
Location
Wydaho
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.

 
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Herzog

somewhat damaged
Admin
Location
Wydaho
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.
 

Mouse

Trying to wheel
Supporting Member
Location
West Haven, UT
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

Burn-barrel enthusiast
Supporting Member
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.
 

Herzog

somewhat damaged
Admin
Location
Wydaho
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

somewhat damaged
Admin
Location
Wydaho
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...

IMG_6842.jpg
 

TRD270

Emptying Pockets Again
Supporting Member
Location
SaSaSandy
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 live my life 1 dumpster at a time
Location
So Jo, Ut
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! 😬😕

IMG_6453.jpeg
 

Kevin B.

Not often wrong. Never quite right.
Moderator
Location
Stinkwater
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?
 
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