What causes the cylinder head to crack

It's made from aluminum, it expands and contracts a lot as the engine warms and cools, and acids develop in the coolant. The anti-corrosive additives in antifreeze wear out in about two years. That's why it must be replaced every two years. That acid contributes to leaking head gaskets, not cracked cylinder heads. Regardless of the cause, cracked cylinder heads are common on any car brand.

Any overheating would expediete the process and might cause the head to crack immediately.

I am ok.Good answers.