I am pretty sure my engine compartments are well protected, no oil leaks (gasket changed), CVTF is serviced earlier than usual mileage and fitted with Hayden CVT cooler (no more whining noise when using sports mode). On long drive everything is just nice.Since almost all u change. Need expert dy.
At least u know it happened after the replacement as stated.
Years ago i have this symptom too. Old sentra Aircond intermittent hot/cold. Until one day whole engine overheat. Block crack. End up all my mistake and learned from it.
Not mean to scare you. Just share my experience.
i think you have different situation.
What causes your engine crack ??
Thanks,
Ken