broken crank?

[punkmechanic]

here is a video of the engine in my cc at the moment. Im gonna pull it tonight or tommorow and get the truck running with another engine, then tear into this and see what is up.

http://www.youtube.com/watch?v=GeyoP2ZmdNE

Any ideas?

punk

 

[CESMITH]

Thats not right

 

[hesutton]

I betcha it's *****'ed.

Heath

 

[THECACKLER]

I've seen Harmonic Balancers "walk" off the Woodruff key, but only twice and those were SBC's. It screws up the crank key way but can be welded and re-cut. Also seen the outer mass of the HB spin on the rubber and roll it up to one side, making it eccentric but again on Chevys.. Broken cranks at the snout will do what is seen but usually make a very low frequency knocking, like a sledge hammer on concrete. Do you have end play on the crank snout? Either way I'd pull the balancer before the engine just to be sure.

 

[Diesel JD]

IDK Justin it will be interesting to see what you find. I would just imagine if the crank was actually broken it would not run at all or something would find it's way out of the block, but then I'm a novice you're the real diesel mech. We went a long time never seeing a broken crank but then Todd C had one. That's the only confirmed one I can remember through 7-8 years of trolling these forums and TDS. Could it be something like piston slap or bad bearings?

 

[funnyman06]

Something isn't right there... if the crank actually broke i wouldn't think it would continue to run, wouldn't it just kind of die a painful death?

 

[janos1]

Definitely broke, prolly after the first of crank throws IMHO. Seen 'em broke after the fact but never seen one broke and run.

 

[dyoung14]

WOW yea there defintley something wrong going on, broke crank is a good possibility

 

[typ4]

Holy crap you werent kidding, I should have looked at it yesterday when IWas there.

It is broke thru the first counterweight I bet. I have a crank
I bet the oil pump gear isnt happy.

 

[icanfixall]

Well its going to be a funny break. Something that will fall apart when you remove it. The oil pump gear is probably holding things in line but not for long...

 

[NapaBavarian]

Drive it down here, let me take a look...

 

[THECACKLER]

Heck yeah they'll run with a broken crank. That's how I know what they sound like. The first time I saw one was when I had a customer drive it in. It was broken from the edge of the center main diagonally through the counterweight. That's what happens when the crank is not ground correctly. Too far under sized or too little fillet or radius at the edge of the journal. More often it's from a bad Harmonic Balancer. The HB is actually a torsional dampener that serves to dissipate the harmonic vibrations that occur as the engine fires. Most people don't realize that the crankshaft continually twists as it revolves. Each crank pin moves ahead of it's set position each and every time that cylinder fires. To look at a massive crank shaft it's hard to believe that it bends, but if you want a reality check, walk into a decent machine shop and ask why they stand the crank shafts upright. If they're on the ball they'll tell you they bend if you lay them down.
I've also seen it from a momentary lapse of oil flow to a main causing it weld to the crank just long enough to spin the main in the block a few degrees and creating a misalignment of the oil supply hole to the bearing. This creates a doomed bearing which won't show up as low oil pressure but it is constantly dragging on the crank. Ain't engines cool? Ain't failure analysis cooler??
I really want to see pictures of the carnage when it's identified, but I'm still rooting for it to be just a bad balancer.

 

[Mat J]

just got to say im a rancid fan myself. it will be interesting to see whats up with the engine it sure dont sound to happy.

 

[BigRigTech]

I know a guy locally who had a 7.3 crank break in his wrecker...He was climbing a steep grade hauling a truck on the back and it let out a bang and that was it.......Done like dinner.

 

[punkmechanic]

The balancer appears solid and intact. I had this engine on my shop floor before install and aside from some play (twisting, like gear lash) its solid in out and every direction.

Im dying to see just went ( drastically) wrong.

Punk