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  #1  
Old November 6th, 2017, 11:16
anthrax323 anthrax323 is offline
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In-vehicle rod bearing/wristpin replacement?

As luck would have it, right after I get my 2001 XJ back on the road, I've developed a significant rod bearing or wristpin knock... It'd been around in some form for about 10,000 miles, and would largely go away once warmed up, but after accelerating to pass someone on the highway the noise became MUCH more substantial.

I know that rod bearings are easily accessible just by dropping the oil pan, but I'm more afraid that it's ultimately a wristpin failure. Is there enough room to pull the pistons down from the underside (with the crankshaft still in-place) so I can replace the wristpins too? Or would I be looking at pulling the head at that point?
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Old November 6th, 2017, 11:41
RCP Phx RCP Phx is offline
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Re: In-vehicle rod bearing/wristpin replacement?

You have to pull the head.
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Old November 6th, 2017, 13:17
anthrax323 anthrax323 is offline
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Re: In-vehicle rod bearing/wristpin replacement?

Looks like lifters are going on the list too then. Thanks man.
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  #4  
Old November 7th, 2017, 22:16
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BCKNBLK BCKNBLK is offline
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Re: In-vehicle rod bearing/wristpin replacement?

Agreed, you have to pull the head, which is fairly straightforward. Keep in mind though, that it would not be wise to replace these items for just one cylinder. You are far better off replacing the bearings and/or wristpins for all of the cylinders. If the engine has not been opened up before, you most definitely are in for a surprise or two. How many miles are on it?
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Old November 8th, 2017, 22:03
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8Mud 8Mud is offline
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Re: In-vehicle rod bearing/wristpin replacement?

Why not pull the pan, inspect the bottom of the pistons. Have somebody rock the harmonic balancer bolt and watch for play between crank movement and piston movement, You'll likely be able to see significant wrist pin slop (or hear it).

My bet is connecting rod bearings, I've had to swap them out on three different XJ's so far. I have found loose rod cap bolts. I plasti gauge mine, top and bottom of the bearing. The top bearing seems to wear quicker (more) than the bottom does.

A little tip, take the pan off, liberally spray down the whole bottom of the motor with brake cleaner, let it drip and dry overnight. Trying to do it with oil dripping in your face sucks. Tip two, plasti gauge melts in oil, rods, caps and bearings have to be squeaky clean. Tip three, a little loose is netter that too tight. Trying for perfection with over sized bearings is likely unnecessary, a thousandths larger than optimum clearance isn't going to hurt anything. Tip four, check the right side of your block for over sized bearing codes.

Getting the pan off without screwing it up can be a pain, it will save time in the long run if you don't bend the pan lip up too much.

Last edited by 8Mud; November 8th, 2017 at 22:08.
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Old November 9th, 2017, 16:09
anthrax323 anthrax323 is offline
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Re: In-vehicle rod bearing/wristpin replacement?

Thanks for the tips, guys.

Where exactly on the block are the bearing codes? Assuming near the bottom on the passenger side, but thanks to bad oil filter adapter O-rings, there's at least a 1/8" cake of mess all over the place. Narrowing it down will save some digging.

I'd forgotten that I bought a new oil pan gasket and RMS a few years ago (when I planned on fixing the latter), so I'm good to go other than buying the bearings.
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Old November 9th, 2017, 17:04
RCP Phx RCP Phx is offline
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Re: In-vehicle rod bearing/wristpin replacement?

There are no codes on the block, any machining that would ever be done(besides boring/decking) are done to the crank.
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Old November 9th, 2017, 21:19
Jeep Driver Jeep Driver is offline
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Re: In-vehicle rod bearing/wristpin replacement?

Quote:
Originally Posted by RCP Phx View Post
There are no codes on the block, any machining that would ever be done(besides boring/decking) are done to the crank.
Yes there are.

Over/under codes on some engines.

http://street2mud.com/webfiles/AMC%20Engine%20codes.pdf


May not be common today but it certainly was not that long ago.
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Old November 10th, 2017, 08:21
RCP Phx RCP Phx is offline
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Re: In-vehicle rod bearing/wristpin replacement?

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Originally Posted by Jeep Driver View Post
Yes there are.

Over/under codes on some engines.

http://street2mud.com/webfiles/AMC%20Engine%20codes.pdf


May not be common today but it certainly was not that long ago.
Worthless! Where's anything that applies to Cherokee's or Comanche's?
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Old November 10th, 2017, 08:40
anthrax323 anthrax323 is offline
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Re: In-vehicle rod bearing/wristpin replacement?

I'll be picking up a proper micrometer set, so no big deal on the tag. Given that it's a 2001, they might have refined their manufacturing process to the point that tagging for over/undersized bearings became unnecessary.

That being said, tolerances should be ideally between 0.001 and 0.0015" right?

*EDIT* - Everything I'm reading points to:
Desired: 0.0015"-0.002"
Allowable: 0.001"-0.003"

Here's to hoping the damn journals aren't f***ed.

Last edited by anthrax323; November 10th, 2017 at 08:44.
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Old November 10th, 2017, 09:53
RCP Phx RCP Phx is offline
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Re: In-vehicle rod bearing/wristpin replacement?

No real issues either way, you can have your crank turned or possibly get a exchange crank. We accepted as a good core anything to .030" under, after that we would just weld-up the journals and start again!
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Old November 10th, 2017, 11:10
Green XJ Jeep Green XJ Jeep is offline
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Re: In-vehicle rod bearing/wristpin replacement?

Quote:
Originally Posted by RCP Phx View Post
Worthless! Where's anything that applies to Cherokee's or Comanche's?
A different letter represents each part and the modification. The letter is located on the boss directly above the oil filter on six cylinder engines, on the valve cover tag on V8 engines. One or more letters may be present:
B- 0.010" oversize cylinder bore
C- 0.010" oversize camshaft bearing bore M- 0.010" undersize connecting main bearings
P- 0.010" undersize connecting connecting rod bearings
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Old November 10th, 2017, 12:26
anthrax323 anthrax323 is offline
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Re: In-vehicle rod bearing/wristpin replacement?

Quote:
Originally Posted by RCP Phx View Post
No real issues either way, you can have your crank turned or possibly get a exchange crank. We accepted as a good core anything to .030" under, after that we would just weld-up the journals and start again!
Yeah... If the crank needs machining, the engine needs to come out. If the engine comes out, an LS2 is going in its place. I'm just hoping it's good so I can limp the engine along for a month or two until the garage is finished, and funds are available for the LS2 swap.

I picked up a 2001 M5 a few months back, so now everything in the stable needs at least 400hp. Because reasons.
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Old November 11th, 2017, 08:35
RCP Phx RCP Phx is offline
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Re: In-vehicle rod bearing/wristpin replacement?

Quote:
Originally Posted by Green XJ Jeep View Post
A different letter represents each part and the modification. The letter is located on the boss directly above the oil filter on six cylinder engines, on the valve cover tag on V8 engines. One or more letters may be present:
B- 0.010" oversize cylinder bore
C- 0.010" oversize camshaft bearing bore M- 0.010" undersize connecting main bearings
P- 0.010" undersize connecting connecting rod bearings
That is a AMC document which means it might apply if you own a 84-86!
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Old November 11th, 2017, 09:03
Jeep Driver Jeep Driver is offline
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Re: In-vehicle rod bearing/wristpin replacement?

Quote:
Originally Posted by RCP Phx View Post
That is a AMC document which means it might apply if you own a 84-86!
There you to being arrogant again.


Chrysler bought AMC in '87 and continued using AMC parts through '89. Chysler didn't retool until '90 (IIRC).

I had a '89 that was a mixed bag of AMC and Chrysler parts.

No, may not apply to the OP's 2001, but the OP brought it up. Your blanket statement that it does not apply to XJs is incorrect.

The entire world does not revolve around the OP, nor you. Others may read this that do have an AMC........just a point of interest.


As for the OP's desire for a cheap-out in-frame...........waste of effort. He's 90% of the way there, pull it and rebuild it.


As for welding up a journal? 4.0 cranks are still dimes-a-dozen, another dumb idea.


And further, at this point, it would not be uncommon to find any year block in any year XJ.

Last edited by Jeep Driver; November 11th, 2017 at 09:07.
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