4.0 Engine Knock

RRADFORD9ER

New Member
Joined
Dec 3, 2006
Location
Asheville
I've been battling a slight tick at cold startup in the WJ for about 6 or 7k miles. Tried various oil additives like Rislone, MMO, and Lucas which didn't really help. Cranked it up a couple of days ago and it was MUCH worse.
aimg.photobucket.com_albums_v366_rradford9_th_VID00046.jpg

I was over at Chris's (novacayne75) house to work on my LA's and at his advice, left it there for him to drop the oil pan and try to figure out whats wrong. Based on other WJ 4.0's I've seen make similar noises I'm guessing at least one of the piston skirts has broken.

Should find out for sure out later today...Any ideas from the video?
 
I'm not much help on Jeep 6's, but check the simple (stupid) stuff first... like make sure the flexplate bolts are tight! It will mimic a bottom-end knock that sounds like the motor is blown!
 
Caver Dave said:
I'm not much help on Jeep 6's, but check the simple (stupid) stuff first... like make sure the flexplate bolts are tight! It will mimic a bottom-end knock that sounds like the motor is blown!
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aren't you the one who spotted that on that dude Eric's AK Postal Scrambler one URE run a few years back? IIRC, that was a Jeep I6 258. Everyone thought the bottom-end knock was the end of his engine...pulled off the inspections plate and found the offending flexplate bolt(s)...motor saved!
 
Have you tried a stethoscope?

It was an oddball scenario but a neighbors friend thought his engine was on the way out. It wasn't a real knocking noise, but it was similar. Traced the noise to the PS pump. Removed the belt and no more noise....
 
Used a long pry bar held up to the ear and definitely sounded like it was coming from the bottom end.
 
Found 1/4 of the #4 piston was gone! Will have to completely tear it down to see if the cylinder walls are damaged and whether or not I can use standard size pistons or have to bore it out and go up .20 or .30...
 
aimg.photobucket.com_albums_v366_rradford9_4Piston.jpg
 
What was the mileage on that unit? Any signs of the up and coming damage? Or how tight a maintenance schedule was maintained? Not being nosey, I just got a 4.0 daily driver showing 135K and was wondering how much life I might be looking at. Mines not noisey but it seems everyone I've ever been around after about 125K develope some quirks.
 
i had that problem in one my my old jeeps. I rigged a switch to kill power to the coil and would crank for about 30 sec to get the oil going, then flip switch and start it up and it would start up much much nicer without the knocking and helped the engine to last a long time
 
WARRIORWELDING said:
What was the mileage on that unit? Any signs of the up and coming damage? Or how tight a maintenance schedule was maintained? Not being nosey, I just got a 4.0 daily driver showing 135K and was wondering how much life I might be looking at. Mines not noisey but it seems everyone I've ever been around after about 125K develope some quirks.
Click to expand...
Other than a slight lifter tick, most 4.0's should last past 250k miles MIne ran good at 216k, but i opted for a stroker as a pre-emptive strike!
 
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