In the cylinder block of an engine including a heat storage apparatus, a water jacket is formed between a cylinder bore wall that forms a cylinder bore and a cylinder block outer wall. An actuator is installed on the cylinder block outer wall. A container is housed in the water jacket. A coolant temperature sensor is installed on the upper portion of the container. An ECU determines the state of a heat storage agent in the container and the state of the container, based on information on the temperature of coolant determined by the coolant temperature sensor.