New Here, just saying hello and seeking info.. Broken Crank

Hello everyone im new here. Found my way here when reading about my 5.9 common rail.

Recenty broke the crank in my almost stock 2005..
Had my transmission rebuilt due to the welds breaking for my flexplate to torque converter bolts. After upgrading and rebuilding about 500km later thought the flexplate had failed again so i drove it back to the trans shop only to find out i had broken crank somehow.
Didnt do any damage so i found 12 valve crank and rods to install instead. Top end and everything looks great.
Ordering a cam and nozzles soon.
No better time to start really modding my Cummins!!

:woohoo:

Welcome. Damn....how in the hell did you manage to break a crank on a stock motor? You should get some sort of prize for that. LOL

Believe it or not, I've had a few cores come in with broken cranks, my latest was a 2012 6.7, with well under 100k, that broke on the arm between 5 and 6.

I had one 5.9 a couple years ago that broke across a rod journal, tore up the rod bearing, tossed the rod, then the crank wedged apart, splitting the block, breaking 3 main caps and blowing the side out of the block.
It was a stone stock 305 horse 2003 6 speed engine.

I think Cummins CR cranks are extremely hard and sometimes surface fracture, then it spreads, which is why knowing how to properly machine them is such a critical step.

They are so hard, that I've had them come in totally rusty, from sitting outside for a year and they only needed to be cut .010-010.

Mark.

Only thing i can conclude about breaking the crank is a combination of a sloppy thrust bearing and some harmonics from the torque converter tabs breaking and vibrating causing fractures. It was broke between thrust bearing and number 6 rod journal. But even after driving it with broken crank it still had only minimal wear on those bearings. Was only a few degrees play when moving flexplate back and forth.
Only notable symptom was my serpentine belt would squeal when running but stop squealing when put into rev or drive.. I had checked replaced tensioner greased pulleys and replaced belt. Didnt think to check crank thrust. Expected to find that bearing in the oil pan but it was still in place. Maybe some minor wear showing on crank. Possibly enough to cause fractures to start.
Regardless i got off lucky and im confident in the 12valve parts.
Should i have the 12v rods peened and polished before installed? May never go above 500hp.. Or maybe will.. Hmm
Just ordered a Colt Stage 3 and going for some DDP 50hp nozzles..

We've had a bunch of Cummins ISX cranks break.

Check your convertor to flexplate endplay, especially if the thrust bearing was beat up.

Heres some broken crank pictures..

Now please realize ive never torn into a Cummins engine before.. I have the engine turned over and crank removed. Then i slid the piston down the bore and turned 90 degrees. Removed C clip and pushed wrist pin towards the cam side of engine. Yes there was enough clearance. I did this on Cyinders 6 5 4 3 before i got to #2 and realized there is more block casting below that main journal and i couldnt simly swap rods like this as i thought. I WILL have to pull the head to swap rods. I really didnt want to pull the head.
So my question now is .. I can still put those 4 rods back in. But should i trust them after the vibrations from the broken crank?
Either i run the CR rods on a 12 valve crank and not even pull the head. Or pull the head and go for the full rebuild.
Im assuming if i pull pistons i might as well relpace them and rings and rebuild head and EVERy thing while im at it.
Simply droping in a crank and running it is alot easier and cheaper at this point.