2002 TJ 4.0 Engine Locked?
- Thread starter Jimmy's Jeeps
- Start date
Airjunky
TJ Enthusiast
I have been going down this road on a TJ that I bought last fall. Drove it most of the winter, then one day, coming home from work, 116k miles, and I have a horrible engine knock. After a week or so of looking, I finally found the problem under cylinder #1.
I've had this same thing happen on a little Dodge Neon 4 cylinder a few years ago. I chose to go the route you did & just replaced the rod bearings. It worked fine in the end, cost me like $20 & a Saturday to get it done. I sold the car with another 10k miles on it, still running fine.
But the Jeep crank had a little wear on it from the bearing above. And frankly, I wanted to keep the Jeep for a while. In the end, I chose to rebuild. We plan on completing assembly & reinstall of the rebuilt motor this weekend.
I've had this same thing happen on a little Dodge Neon 4 cylinder a few years ago. I chose to go the route you did & just replaced the rod bearings. It worked fine in the end, cost me like $20 & a Saturday to get it done. I sold the car with another 10k miles on it, still running fine.
But the Jeep crank had a little wear on it from the bearing above. And frankly, I wanted to keep the Jeep for a while. In the end, I chose to rebuild. We plan on completing assembly & reinstall of the rebuilt motor this weekend.
The left one is always the .001 bearing. And the first picture came out darker for some reason. These are the 2 worst bearings, the others show less overall wear.
The single .001" bearing that I ordered says 'undersized'. Is that right? Is that the way the industry refers to them? I thought I needed .001" thicker. Maybe it refers to the crankshaft size....
Sorry, just trying to make sure that I don't have to do this job 3 times...
Sorry, just trying to make sure that I don't have to do this job 3 times...
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Correct! It refers to the crankshaft.
During rebuilds, it is common practice to re-machine the crankshaft by 0.010", 0.020", etc. So after machining the crank is undersized compared to the original dimensions. And your new bearings have to match the undersized crank.
I don't know how old your Jeep is but my guess is that 0.001" undersized bearing was installed to compensate for excessive wear on that pin. I would mike that crank pin and see what it measures compared to the others. That could be the source of your knock. I don't know what bearings are available but you may want to go more than 0.001" on that bearing.
If you do the clearance check with plastigauge as suggested, you'll know but you can probably determine if you are in the right ballpark by measuring.
Do what @g.hayduke suggested. The bearings you posted look fine. Bearings are sold in pairs. So you will get two .001 shells to make one complete bearing.
Good choice. There’s not a chance in hell that new bearings would have worked with how long that rod bearing hammered. Note to future people reading this thread. If you ever hear a rod knocking turn your engine off immediately. Have it towed. Do not drive it.
Exactly. I did what you said and ordered a STD complete set, plus 1 pair of .001". In my removed bearings, there is only 1 .001", all the others are STD. It seems a bit weird doesn't it?
Never heard of that. They need to be a matched pair. Maybe they were wanted .0005 and had to do it that way. Use plastigage on that one for sure.
Hey guys, I finally received all of the necessary parts to redo the job. Question: when using the Green Plastigage, what is the tolerated number range for a properly fitted bearing?
Thanks for your help.
Thanks for your help.
Cool. Now seeing as I can only get the Plastigage under the bottom bearing. Do I absolutely have to test top and bottom bearing with Plastigage? Or is bottom good enough?
Thank you very much. Unbelievable how much aggravation can come from missing a few numbers on a part...
Gentlemen, I Thank You so Very Much for all of your input. I found the time to finish up the job earlier today. It was in fact the oversize bearings that were at issue. Now she sounds like she has a brand new engine. Not one undesired sound, just solid engine. Thanks again. Be well!
The Goblin
Member
Thanks for sharing all this. Question for you, did you have any other bearings that looked worse than the ones you posted here in the picture? Those bearings didn’t really look bad so it would surprise me if that was where the knocking was coming from.
Did you try the plastigauge on the old bearings? Or just the new ones you got?
I have a knock I’m trying to figure out too (in another thread) but the clearances on my old bearings look just fine with the plastigauge.
So I’m just wondering what exactly it was that you think was causing the knock. Thanks man! Glad you got it solved!
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