toolman946 via CraftKB.com wrote:
You guys may find this interesting.

A number of years ago a friend of mine was the Service Manager for a large
Caterpillar dealer. They began having fracture problems with grade 8 bolts
(or maybe grade 8 studs) on the diesel engine oil pans. They replaced
numerous oil pan bolts and they still kept breaking.

Ken (my buddy) while not being trained as an engineer was a pretty sharp guy.
He noted that the shop had begun to use automotive silicon in place of the
composite oil pan gasket. He thought that the silicon was allowing the oil
pan to "float" slightly causing a high frequency vibration that was inducing
stress fractures in the grade 8 bolts. He ordered the shop to resume using
the original gaskets and the problem never recurred!

His theory made sense to me. What do you think?

It seems possible that the bolts were cracking as a result of fatigue
cracks growing slowly due to the vibration. But I suspect this could
only happen with a very rubbery gasket material.

Best wishes,

Chris