Sounds like the rod journals were turned down 0.25mm..... not good at all according to Mitsubishi's TSB.

This is the first anecdotal evidence I've seen that the TSB should be taken as Gospel - there has been some speculation that the crankshaft can be reground and the radius reworked..... even one of my local machinists thinks it can be done. Maybe on this one, they didn't try to grind the fillet radius back to the same relief relative to the journal, but who knows.

After seeing this, I doubt I'll ever try to grind one of these crankshafts to find out if it can be safely done.

It also should be a lesson to anyone who considers buying a remanufactured 3.0L engine. Thanks for posting it.

If the color of the rods looks ok - with no blue discoloration - and if they are checked for length, twist and thickness - you should be able to rebuild the engine with a replacement crankshaft and bearings..... but I'd also want to inspect the saddle area of the block around the mains and the girdle for discoloration and wear. The pistons and wrist pins should be carefully inspected as well.

Frank

If you reuse the block, get the line bore checked. I would guess that there was a large amount of stress on the mains once the crank broke.

Hard to tell but as others pointed out the radius looks suspect and or this is the reason for the TSB. I wonder if that one journal may have been welded. A close up of a good rod journal and a bad one would be interesting.

The up side this is the snout and the keyway for the front pulley look really good. <img src="/forums/images/graemlins/rodent.gif" alt="" />



Kevin

Hmmm.

Whats the deal with that dipstick??? Bent when you opened it up or bent when you pulled the engine and set it down?

the dipstick is not bent
i thought it odd where it was i pulled it out and put it back in and it went to the same spot

it appears there is no other damage
no discolorations or where marks on block or cradle or rods
the crank measures
rods 49.5mm
block 59.5mm
not sure what factory is

The dipstick is where it should be - it has a manufactured twist on the end.

Factory specs are:

60mm for the mains
50mm for the rods

Your crankshaft main journals have been turned down 0.5mm. Your rod journals have also been turned down 0.5mm - which doesn't match the installed bearing size of 0.25mm unless I'm making an incorrect assumption based on the bearing mark.

A loose fit like that would allow the crankshaft to flex and pound the rod bearing...... and the pounding might eventually hammer the crankshaft......... until it broke at the weakest point - which is where they ground off the stress relief fillet radius..... and is the approximate fulcrum of the force exerted by the piston.



If you want to try rebuilding that block to save money, you might be ok with just a replacement crankshaft..... but I'd be leery of it and would get as far away from it as I could........ then I would quickly turn around and shoot it before it had a chance to jump back into my truck.

Frank

what is the factory MM on the block and cradle

I haven't seen a spec on the main saddle bores.

Frank

Although not directly related to this crank,
Were gonna see alot more cranks cracked in half in all new cars from now on cause, here I go again, Bubbles in Chinese metal...

That thing broke exactly at the ex-fillet.

I would NOT reuse that block if I could help it. It's got the bad hoodoo in it. Find a seasoned short block from the jy and mini build that. Find one of those forged cranks FrankR found...

I think Frank has only found bad cranks in the yards. That's why I was looking on RockAuto at the DOHC forged cranks under 3000GT. But their cranks are "remanufactured" ,too, so I wouldn't want a cast crank, maybe you can't machine the DOHC forged either...