Documenting My Crank Walk - Jeep 4.0

[BALTANAKT]

Greetings all. Thought I'd create this thread to help others in the future.

The Basics

• Purchase Jeep in Fall
• 1991 XJ 4.0HO
• 130K
• Engine running great, good power, great mileage
• Winter - Belt started squealing
• After checking everything I was mystified
• It turned out crank was walking 3/8", throwing the harmonic balancer pulley out of alignment

See video of crank walk here: https://youtu.be/L4XN_mSOk_o

What to do?

• I debated pulling the oil pan to try to replace the thrust bearing.
• Found video on youtube with exact same symptoms
• Turned out the guys crank was destroyed at the thrust bearing
• Decided there was a good chance mine was also destroyed

Pulled my engine

• Found shards of copper thrust bearing in bottom of oil pan even though oil came out clean
• Discovered my crank had a massive groove worn in it from the thrust bearing
• Thrust bearing is also destroyed

See images here: https://drive.google.com/drive/folde...US?usp=sharing

So what caused the carnage?

• I am not sure
• The coolant bottle is very dirty
• Could have been a head gasket leak at some point ruining the lubricity factor
• Could be the oiling grooves on thrust bearing were not milled enough
• Could be a ballooning torque converter
• Could be high pressure in the transmission lines (so I've read, and my pressure was high)

As it's been difficult to find the culprit, I am doing what I can and crossing my fingers. Replacing engine and torque converter. Also had transmission line pressured adjusted back down to where it is supposed to be.

I wonder if these bearings or crank were original? There was a number paint markered into the back of the crank where it meets the flex plate. And two marks on the thrust bearing cap.

Hope this next engine survives and that this will be helpful for someone down the line.

[Ecomike]

I would not trust the 130 K miles reading, the gauge assy could have been swapped out. Sounds way too low for a 91. Sounds like some small piece of metal thing failed and did the damage but I am not the expert of the guts of the crank area. Or PO let it run out of oil and it did the early damage before you bought it then it failed later.

[blu3fan]

Honestly. after my experience with a shop my friend said did good work. I can say maybe the engine was rebuilt. or like said above. ran wrong
I took my engine to b&b automotive in mesa arizona.

first the guy told me he could not fix my head without destroying it.
. I should have gone and picked them up right there and then.
not only did they grind the crank journals to two different specs.
but they ground the trust bearing as the wrong one.....
oh and this took them 4 weeks.


end all if you did not build it. you do not know what happened.
could be morons like the shop I went to.

[BALTANAKT]

The Jeep is in great shape for its age so I believe the mileage.

The possibility of the engine having been rebuilt is very real.

I've never seen paint marker on original engine parts.

[burntkat]

If there's paint marker, it's likely a junkyard pull. All bets are off. Best to yank it and rebuild it.

[trippled]

I have seen paint markings on factory engines.ita not uncommon. But there's also junkyards that do the same. Without seeing it's hard to see.your pics aren't working for me, it says I need permission?.

There's also the possibility that the bearing just failed because it failed. If there's not a lot of evidence of failure, like multiple failed bearings from low oil, it's totally possible the thrust bearing was defective from the get go.

[Ecomike]

I agree, but used good working pulls are soooo dirt cheap, I would not bother trying to rebuilding that one. I would just swap it out for a known good used engine.

Originally Posted by trippled

I have seen paint markings on factory engines.ita not uncommon. But there's also junkyards that do the same. Without seeing it's hard to see.your pics aren't working for me, it says I need permission?.

There's also the possibility that the bearing just failed because it failed. If there's not a lot of evidence of failure, like multiple failed bearings from low oil, it's totally possible the thrust bearing was defective from the get go.

[BALTANAKT]

New motor is going in this weekend.

Sorry about the images. Had to take a moment to find an alternative to photobucket. I did just that and the images are below. Crossing my fingers that this works.

[Ecomike]

Is that the crank shaft that wore down instead of the bearing????

[BALTANAKT]

First photo is the crank that got worn down.

Second is the wear side of the bearing.

[HttpWayne]

Crank walks 3/8" ?! It shouldn't move a millimeter. You got big problems if it's moving that much.

It's time for a new engine and to put that one on the back burner for a rebuild in the garage somewhere. You're going to need a good machinist to inspect both the crank and the block. And the cam, if you plan on keeping it. It ain't moving that far without contaminating the oil with metallic debris.

... my god, are those Clevite bearings really from 77 AD? I didn't know they were in business that long. I didn't even know bearings existed back then

[burntkat]

Great googly moogly. Resize much?

[burntkat]

Since the bearings are marked 2-97, it is abundantly apparent this engine has been rebuilt at some point in the past.. and apparently, poorly.

I'll bet they didn't check the crankshaft end play, set it up too tight. It wore in, and the wear metals set up an accelerated wear throughout the system, but especially there.

Block and journals most definitely bear a complete, and close, inspection. Someone made a good point about good used pulls being cheap, but even then it's a bit of a crapshoot. That said, I will be doing the same in my 90, shortly.

[blu3fan]

wow. thats the worst crank I have ever seen in an xj.
And I ran mine with about 1/2 oil for 2 weeks when I first got it. I was 17 and uneducated.
you want to get it looked at by a machine shop before you throw any more money at it.

[BALTANAKT]

Does 2-97 = month-year? Trying to understand how we know for certain this was rebuilt.

I'm currently swapping in another motor in.