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1G 6-bolt crankwalk - unprecedented 0.065" endplay

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sacrileger

Proven Member
288
43
Jun 26, 2016
Orillia, ON_Canada
I could not resist buying a 1992 n/t, 5spd Talon w/ 100K miles on it for $400. Lady owned since new and she kept all receipts since the day she bought it. The driver side frame was completely gone but the motor appeared to be in excellent shape. I checked the compression, 174 - 169psi hi to lo, and leak down test was on average 8% loss. I rechecked compression and leak down in my garage and got the same figures. The engine starts, runs and revs like new. Simply exceptional mechanically. I took the engine out and was going to drop it into my other project car once I changed timing belt, timing gears and clutch. I noticed the wheels were turning at a good clip when the car was propped up and idling in neutral. I figured the clutch was dragging.

As I was taking the belts off, the crankshaft moved outwards. I rechecked and could not believe it:
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Once I took the cover off, I put a dial indicator to it and measured 0.065" endplay:
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I think this is a severe case of crankwalk! The thrust bearings are probably gone. Given the history of this car/engine, I am completely ruling out thrust bearings failing due to assembly mistake, misalignment, oil starvation, contamination/dirt, abused or neglected engine, not finished crankshaft thrust surface, faulty
crankshaft surface geometry, etc. but I am betting that the lady was either riding the clutch pedal or the clutch was not properly adjusted which could've held the throw-out bearing against the pressure plate and putting forward pressure on the crank, pushing against the rear side of the thrust bearing; thus, destroying the bearings. The spinning wheels while in neutral would be a good indication not all was ok.

My question is this: what is the diagnosis and what wall thickness are the thrust bearings? I hope it is not metal on metal at this point with 0.065" endplay. Can there be any other explanation?

I have looked at these thrust bearings but cannot make out the wall thickness from their data:
https://tinyurl.com/y7w5cg7k
https://tinyurl.com/ybulc6d6

How severe is 0.065" endplay and is there a chance some of the bearing will be still left there?
 
At .065" crank is junk for sure. But pull it apart and see
is that because the sidewall of the thrust bearing is less than 0.065" thick?
I would have expected the engine not to start, or at least run funny, if the crank was grinding against the block. If the crank is toast, what about the block?
 
Crank is toast, block may be. With a 6-bolt there is no crank sensor to get destroyed and stop the car from running.

I am considering selling the motor and not taking it apart; thus, these questions. What surface on the crankshaft is damaged with 0.065" crankwalk?
I did a quick search and it appears that this poster had 0.058" endplay, yet still some thrust bearing left; at least by looking at those pics:
Crankwalked 6-bolt, pics and questions on 2.3 stroker build

His crank is toast due to different reasons, not due to the clutch putting forward pressure on the crank; thus, wearing the bearings down over a very long time. Perhaps I am thinking that unless the crank wears the bearings down and makes contact with the block, it all should be ok. It would all depend on the thrust bearing wall thickness. Would that not be the case? For as long as the thrust bearing, no matter how thin, is still there, there would be no reason why the crank would be torn up at that particular place. Is the crankshaft making contact elsewhere? Is that what the missing piece is for me?
 
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Pretty much but like stated above remove the oil pan and check it. One of my previous engines did this to I never measured the endplay with an indicator but it's close to what you've got going on and there was still backing left on the bearing. There's 2 sides to the thrust bearing so you can have over the bearing thickness and still have some left. Mine failed from fuel contamination with a 2900 clutch. Too much leak down. The crank should be checked for run out on the thrust surface. You can check this yourself by putting in new main bearings and checking endplay in various rotations of the crank. Its definitely worth investigating.
 
...close to what you've got going on and there was still backing left on the bearing. There's 2 sides to the thrust bearing so you can have over the bearing thickness and still have some left.

yes! thank you! I have never run into this so I have no idea what I am going to find in there but my thinking is that for as long as there is some material left between the block and the crank, i.e. the load side of the thrust bearing wall, no matter how thin, the surface(s) of the crankshaft should not be torn and the crankshaft not junk. Improperly adjusted clutch would not cause as much damage as dirt and metal particles. Since this was not a drag car, or abused and revved engine, this would have been a gradual process and the wear down would be "gentle" and even?
Do I detect some hope here...?
 
When my 7-bolt walked my endplay was .063". Ruined the crank & the block. Gauged both out so there was not material for a new trust bearing to install on. Never lost my crank sensor either. Car was still running just couldn't make left turns.
 
When my motor was torn down there really wasn't a thrust bearing left, look more like a main journal bearing & the crank counterweights were pushing back & forth gauging out all the surfaces from trying to stay inbetween all the journals. Making a long story short, my walked block & crank went back to Mitsubishi corporate via regional. Pull the oil pan & check yours out.
 
The crank doesn’t have to hit the block to be garbage. Wearing through a few thousandths of a metal bearing is plenty. I guarantee 100% that the thrust face of the crank is no longer flat.
 
The crank doesn’t have to hit the block to be garbage. Wearing through a few thousandths of a metal bearing is plenty. I guarantee 100% that the thrust face of the crank is no longer flat.

I have never replaced thrust bearings, only worn out, badly seated, rod bearings. The rod bearings were some soft alloy material and were worn out unevenly. I measured the journals diameter w/ a micrometer and they were all within spec (not oval or tapered) while 2 bearings were worn out only on one side.
Are the OEM thrust bearing the same mat'l as the crankshaft? Or the same hardness as crankshaft? If the answer is yes, than I might as well not bother taking the tranny off, putting the motor on engine stand and examining the damage. I am sure I can get $400-500 for the 6-bolt w/ tranny attached as it sits on the floor now. However, if there is a tiny chance that the thrust bearings are softer than the crankshaft and thicker than 0.065" than it makes sense to take it apart and hope... I think the service limit is 0.005" wear before the thrust bearings are replaced. I am just not sure if the 0.005" accounts just for the bearing wear or both (crankshaft and bearings) together?
But if the consensus is that it is 100% garbage then I am not sure if it makes sense to put more time into this...? I am sitting on the fence at this point and not curious enough to see torched and torn metal surfaces.
 
... I guarantee 100% that the thrust face of the crank is no longer flat.
also @bastarddsm - those were very prescient calls. No more hope. I had to know. The crankshaft is garbage. Now I know and share some garage porn with those who are curious.

The loaded thrust face was worn to a sliver
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The wall thickness of the main OEM shell, including the thrust shell, is 1.982 - 1.990mm at the crown of the bearing.

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That translates to (+/-) 0.079" which means with my 0.065" endplay I had about 0.014" left before the crank started hitting the block; thus, my block will be very likely salvageable.

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It would appear this was clutch related, i.e. the pressure plate was putting load on the thrust bearings and wearing them down since the opposite side, facing the front of the engine, was perfect. I could upload pics of the clutch for further diagnosis.

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Once the oil grooves and lining were removed by the constant friction, by that time there would be hard steel running on hard steel with minimal lubrication and very rapid wear of both surfaces. Additionally, the localised heat may well have changed the properties of the crankshaft thrust face.

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Thrust faces can only generate oil films capable of withstanding 1Mpa of load pressure. To fully recondition this face would require grinding below the heat affected zone further increasing the potential end float.

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Hence, is still hope the block is salvagable.
 

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