Shirl:
Yep. I've been teased that my preflights are like 100-hr inspections. I
do everything you listed above, and it didn't stop the oil cooler from
failing.

Mxsmanic wrote:
Was it your own aircraft?

Yes. It's a rare occurrence. When something like this happens, you then
hear accounts from the few who knew of something similar. One such
account was of a NEW oil cooler that failed in its first 3 hours. No way
to predict it. Flushing/Pressure testing at suggested intervals may help
prevent it (I've heard a huge variance in what that suggested interval
should be -- there doesn't appear to be a black-and-white regulation).