Q: What would cause an engine block to crack?
A: A block can crack if the coolant (antifreeze and water mixture) freezes. An engine block has many coolant passageways. If the coolant does not have the correct antifreeze to water mixture, then the coolant is more susceptible to freezing. Coolant that freezes expands. If the force from the freezing coolant inside the engine is great enough, then the block could crack. Use an antifreeze tester to determine whether you have the correct mixture. For most climates, a mixture of 50% water and 50% antifreeze is the best. This mixture will not freeze even at -35 degrees.