Crankshaft bolt is normally torqued to something like 70
foot pounds. Yes, it takes quite a sharp force to break this
bolt loose. However it can be broken loose if, for example,
the mechanic gave the shaft a good quick jerk to move valves
into next position. We don't know why that bolt is loose, but
we do know that it takes a strong rotation with a torque
wrench to loosen it AND that mechanics rotate the crankshaft
by attaching a torque wrench to that bolt. From those facts we
can only speculate.

redeyedevil wrote:
> I do not know about the Accord, but on the Civic the bolt is pretty
> stuck on with a couple (maybe even few) hundred foot-pound, and
> there's no way turning the engine would loose the bolt.