Bad Connecting Rod Bearings? Solution? - JeepForum.com

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post #1 of 22 Old 04-25-2010, 10:55 PM Thread Starter
CrazyIvan888
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Bad Connecting Rod Bearings? Solution?

So, I have a rattle in the bottom of my engine which I'm guessing is a worn-out connecting rod bearing. It rattles at idle, definitely coming from the oil pan.

Is it worth it to replace the rod bearings (I would do all of them while I was in there)? Or will it run for a while as it is?

Also, is there anything special I need to know or anything else I should replace while I'm in there? I did the rear main seal not too long ago, so that should be good.

I'm thinking the rod bearings should be pretty straightforward to replace, am I right?

Thanks,
CI888


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post #2 of 22 Old 04-25-2010, 11:04 PM
moonshinefuel
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You are talking about the wrist pin bearings in the piston, or are you talking about where the rod connects to the crank shaft.
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post #3 of 22 Old 04-26-2010, 12:03 AM Thread Starter
CrazyIvan888
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Where the rod connects to the crankshaft, sorry for the lack of clarity.

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post #4 of 22 Old 04-26-2010, 10:49 AM Thread Starter
CrazyIvan888
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Bump, I gotta know if I should order these parts or not, and if there's anything else I should order while I'm at it! An extra bearing maybe, in case I screw up one?

EDIT: Too late, I jumped the gun and ordered a set. Write-up to come!

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Last edited by CrazyIvan888; 04-26-2010 at 11:00 AM.
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post #5 of 22 Old 04-26-2010, 11:15 AM
ajmorell
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FWIW those are the referred to as main bearings. The rod bearings are the bearings where the connecting rod attaches to the piston at the wrist pin.
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post #6 of 22 Old 04-26-2010, 11:31 AM
JesseOR
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Main bearings are where the crank shaft bolts to the block. What he ordered ARE rod bearings.

Probably a good idea to change them, but Is it a loud 'rattle'(knock) or pretty quiet?

-Jesse-
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post #7 of 22 Old 04-26-2010, 11:59 AM Thread Starter
CrazyIvan888
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It's a noticeable rattling, kind of like "CLICKatikaCLICKatikaCLICKatika.." Audible from inside the vehicle if the radio's off. From the outside, it can be heard at least up to 30 feet away. If I slide underneath the vehicle, it sounds like it's coming from inside the oil pan.

Most noticeable at idle, the sound gets drowned out when I rev up the engine. Not noticeable at all when I'm driving because the RPMs are usually in the 1500-2000 range.

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post #8 of 22 Old 04-26-2010, 11:59 AM
JrMechanic
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Quote:
Originally Posted by ajmorell View Post
FWIW those are the referred to as main bearings. The rod bearings are the bearings where the connecting rod attaches to the piston at the wrist pin.
Not true. These engines have no bearing at the wrist pin. Most stock engines use press fit pistons in which the wrist pin is pressed into the rod. There is no retainer, or bushing.

Some engines use bushings in the connecting rod and retainers to hold the wrist pin into the piston. This is known as a "full floating" setup. There no "bearing" in either setup.

Connecting rod bearings are the steel shims placed between the connecting rod and the crank journals.

Main bearings are similar to the rod bearings, but have oil ports and passages cut into them and are located on the main journals of the crankshaft.

Replacing the rod bearings is pretty straight forward. Generally you can replace the bearings with standard size replacements, that is if there are no spun bearings or severe enough wear that the crank journal is actually coming in contact with the rod.

Want to swap an NP242 or NP231 into your ZJ? Here's how:
http://www.jeepforum.com/forum/f13/n...pdated-685644/
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post #9 of 22 Old 04-26-2010, 12:02 PM Thread Starter
CrazyIvan888
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Ok, thanks! Will a spun bearing be obvious upon inspection, or is there a special way to tell?

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post #10 of 22 Old 04-26-2010, 12:05 PM
JesseOR
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A bad bearing will be obvious. Check for divots, shiny or discolored spots. A good bearing should be smooth, one color

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post #11 of 22 Old 04-26-2010, 12:06 PM
JrMechanic
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A spun bearing is very obvious. I doubt one has gotten that bad as you would probably hear it. Last time I dealt with a spun bearing was a 86 Olds. I literally heard it knocking from a block away from my shop.

In all honesty, I wouldn't try and change the bearings on your Jeep. Yank the motor and rebuild it or swap in one with lower miles. You've gotten your moneys worth at 245,000, odds are it isn't long for this world.

Want to swap an NP242 or NP231 into your ZJ? Here's how:
http://www.jeepforum.com/forum/f13/n...pdated-685644/
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post #12 of 22 Old 04-26-2010, 12:15 PM Thread Starter
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247,000 now. Gotta update my info.

I can't afford a new motor or a rebuild right now, and to tell the truth I'm actually looking forward to tearing into this thing again. For $30 or so, I see it as a chance to learn a little more about my motor and get some more experience under my belt. Shoot, it's less than most of my friends spend at a bar in one evening!

And if I hopelessly screw it up somehow, the Jeep can sit indefinitely until I can afford a motor or a rebuild (or a new Jeep). I walk to work, so pretty much all my driving is for pleasure purposes.

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post #13 of 22 Old 04-26-2010, 02:35 PM
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Quote:
Originally Posted by JesseOR View Post
Main bearings are where the crank shaft bolts to the block. What he ordered ARE rod bearings.

Probably a good idea to change them, but Is it a loud 'rattle'(knock) or pretty quiet?
My bad guys...I knew that, not sure what the heck I was thinking

Quote:
Originally Posted by JrMechanic View Post
Not true. These engines have no bearing at the wrist pin. Most stock engines use press fit pistons in which the wrist pin is pressed into the rod. There is no retainer, or bushing.

Some engines use bushings in the connecting rod and retainers to hold the wrist pin into the piston. This is known as a "full floating" setup. There no "bearing" in either setup.

Connecting rod bearings are the steel shims placed between the connecting rod and the crank journals.

Main bearings are similar to the rod bearings, but have oil ports and passages cut into them and are located on the main journals of the crankshaft.

Replacing the rod bearings is pretty straight forward. Generally you can replace the bearings with standard size replacements, that is if there are no spun bearings or severe enough wear that the crank journal is actually coming in contact with the rod.
Yeah, oops
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post #14 of 22 Old 04-26-2010, 02:55 PM
bigbill888
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Quote:
Originally Posted by CrazyIvan888 View Post
It's a noticeable rattling, kind of like "CLICKatikaCLICKatikaCLICKatika.." Audible from inside the vehicle if the radio's off. From the outside, it can be heard at least up to 30 feet away. If I slide underneath the vehicle, it sounds like it's coming from inside the oil pan.

Most noticeable at idle, the sound gets drowned out when I rev up the engine. Not noticeable at all when I'm driving because the RPMs are usually in the 1500-2000 range.
i have the same thing going on here. Will watch for your write up.

thanks
Bill

96 ZJ Laredo, 4.0, 242, 230K
95 ZJ Limited, 4.0, 242, 140K
98 XJ Sport, 4.0, 231, 140K
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post #15 of 22 Old 04-26-2010, 08:25 PM
vansskaterfreek
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hopefully your crank and rods are ok... at that mileage and worn bearings like your describing dont be surprised if your crank is ****ed

1998 ZJ 5.9L 122k miles - DD, 242 swap, 3.5" RE, 32" BFG M/T, safari rack, roof-mounted lights, custom steel front bumper with hitch reciever, 10k winch :)
2004 WJ 4.7L 107k miles - her daily driver, 2" daystar BB with scorpion shocks.. not too bad! stuffed 265/65/17 General Grabber AT2'S
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