Case 450b engine idler bolts shear

[rudeag]

Case450b idler gear that drives off the cam to drive injection pump sheared the 2-3/8 bolts in the block. Nothing locked up, engine turns freely and pump turns. Hard to get to so don't want to wrap it up w/o finding cause. Any ideas, thanks for help.

Ran

 

[alrman]

I have seen this happen before ....... quite some time ago.
If the bolts don't look like they were loose, it could be caused by low oil pressure, not enough lube & then the gear twists the post off.
What does the bush in the gear look like, smooth or chewed up a little?
Check also for excessive wear at the camshaft bearings - could be loading the idler gear a little too much.

 

[rudeag]

idler bolts sheared

no movement in cam bushings
idler bushing is free
bolts sheared even with block but can't tell
if they were loose. They have locking tabs
on them, that were still in place.
engine turns over easily
injection pump rotates freely but should it
rotate real easily? thanks

 

[alrman]

Not sure what else to check ....... they are shim adjusted, had anything been done to engine lately?
Injector pumps do rotate freely.
Anything in the sump oil? oil filter?

 

[Tinkerer]

Are you sure they are the correct bolts that are in the gear hub that are shearing off ? They should be 2" long and at least a Grade 5. Before installing the gear back in the engine, put the replacement bolt in the gear hub and visually check that the threads of the bolt extend into the hub slightly. If they are the correct bolts tighten them to specs. with a good quality torque wrench. My guess is that the maybe the sheared bolts were a Grade 2 or they were over tightened , resulting in an extremely weakened bolts. Maybe even too long and bottomed out in the block threads.

 

[rudeag]

I think what happened was that when worked on before they didn't torque
the bolts completely. The threads were rounded off. I gonna chase threads and
lock tight the bolt. They were grade 5 bolts that broke and the right length.
Thanks for helping.

 

[Tinkerer]

Be sure to thoroughly clean the block threads and bolt threads with brake cleaner before applying the LocTite. From what you describe it wouldn't surprise me if those bolts were never tightened down. Just imagine how much that idler was pounding those bolts when the engine was started and shut off ?