An internal combustion engine, comprising: a plurality of cylinder liners defining a plurality of cylinders; an engine block housing the plurality of cylinder liners, the engine block including: an upper planar surface; a cylinder liner coolant jacket below the upper planar surface and in fluid communication with the plurality of cylinder liners; one or more cylinder heads attached to the upper planar surface of the engine block, each of the one or more cylinder heads including one or more cylinder head coolant jackets (60, 62); a coolant cavity in the engine block separated from the cylinder liner coolant jacket; one or more upward coolant passages extending from the coolant cavity to the one or more cylinder head coolant jackets (60, 62) while bypassing the cylinder liner coolant jacket for delivering coolant from the coolant cavity to the one or more cylinder head coolant jackets (60, 62); one or more downward coolant passages extending from the one or more cylinder head coolant jackets (60, 62) to the cylinder liner coolant jacket for delivering coolant from the one or more cylinder head coolant jackets (60, 62) to the cylinder liner coolant jacket; characterised in that the coolant cavity is located below the cylinder liner coolant jacket and in that the one or more upward coolant passages are sized and arranged such that coolant pools in the coolant cavity. a plurality of cylinder liners defining a plurality of cylinders; an engine block housing the plurality of cylinder liners, the engine block including: an upper planar surface; a cylinder liner coolant jacket below the upper planar surface and in fluid communication with the plurality of cylinder liners; one or more cylinder heads attached to the upper planar surface of the engine block, each of the one or more cylinder heads including one or more cylinder head coolant jackets (60, 62); a coolant cavity in the engine block separated from the cylinder liner coolant jacket; one or more upward coolant passages extending from the coolant cavity to the one or more cylinder head coolant jackets (60, 62) while bypassing the cylinder liner coolant jacket for delivering coolant from the coolant cavity to the one or more cylinder head coolant jackets (60, 62); one or more downward coolant passages extending from the one or more cylinder head coolant jackets (60, 62) to the cylinder liner coolant jacket for delivering coolant from the one or more cylinder head coolant jackets (60, 62) to the cylinder liner coolant jacket; characterised in that the coolant cavity is located below the cylinder liner coolant jacket and in that the one or more upward coolant passages are sized and arranged such that coolant pools in the coolant cavity. an upper planar surface; a cylinder liner coolant jacket below the upper planar surface and in fluid communication with the plurality of cylinder liners; one or more cylinder heads attached to the upper planar surface of the engine block, each of the one or more cylinder heads including one or more cylinder head coolant jackets (60, 62); a coolant cavity in the engine block separated from the cylinder liner coolant jacket; one or more upward coolant passages extending from the coolant cavity to the one or more cylinder head coolant jackets (60, 62) while bypassing the cylinder liner coolant jacket for delivering coolant from the coolant cavity to the one or more cylinder head coolant jackets (60, 62); one or more downward coolant passages extending from the one or more cylinder head coolant jackets (60, 62) to the cylinder liner coolant jacket for delivering coolant from the one or more cylinder head coolant jackets (60, 62) to the cylinder liner coolant jacket; characterised in that the coolant cavity is located below the cylinder liner coolant jacket and in that the one or more upward coolant passages are sized and arranged such that coolant pools in the coolant cavity.