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LML ,broken crank

6.2 turbo

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Broken on the first rod journal. It still ran ,but with a knock. Seems like they shouldn't have hollow rod journals,its not a racing gas motor.
 

6.2 turbo

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It's a customer's truck. I had rebuilt this engine about 2 years ago. Never even considered getting the crank magnafluxed.
 

Will L.

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That sucks. Maybe magnaflux would have shown an issue, maybe not. XRay is far better but more expensive.

Cracking often starts on the inside of the hollow section of the journal. You cant see in there when magna-fluxing because there isn’t a good place to set the magnet.

Any other angle pics of the crank? Trying to see a start point, Since it didn’t cross or start at the nicely done oiling supply that is sometimes a source.
 

WarWagon

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Is there a Fluid Damper on this engine? How many miles? Why was it rebuilt? And what do they do with this rig?
 

THEFERMANATOR

FRANKENBURBAN
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Is there a Fluid Damper on this engine? How many miles? Why was it rebuilt? And what do they do with this rig?
Fluidamper has broken several cranks in DURAMAX's, they're too heavy(11lbs heavier than stock iirc), but the ones built in the last couple of years are supposed to be better. Unfortunately this is far to common on LML's than it should be. Seems 11-13 had a pretty high rate of failure at 150k+ miles. It's a crap shoot when the break occurs and it's doubtful magnaflux would have shown anything. GM still refuses to correct the firing order, but L5P's did get several improvements to help. I believe there has been 2 or 3 crank failures in NEW cranks installed with alternate firing order cams, and these were on big HP builds. Unfortunately this happens, the only good news is LML cranks are pretty cheap compared to earlier models.
 

MrMarty51

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Welp, I guess I will know what years of Duramax to stay away from, if I ever would go shopping for a newer wehicle, or an engine to replace the 6.5.
 

WarWagon

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@THEFERMANATOR I was wondering if a FD might have been installed as a possible cause as you have pointed out to us in the past, but, looks like it snaps without one. :facepalm: Guess high mile rebuilds need a new crank to be safe from fatigue failure?
 

6.2 turbo

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It has the stock damper. The truck has around 250 k of heavy towing . The first time it had 5 cracked pistons. It's a fleet vehicle ,well maintained, but gets used hard .
 
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