Water jacket spacer structure

A structure of a water jacket spacer that is inserted into a water jacket formed between an outer wall surface of a wall of a cylinder bore of an engine and an inner wall surface of a cylinder block, the engine having a top dead center side of the cylinder bore as an upper side and a bottom dead center thereof as a lower side, the structure comprising:

• a spacer body member including an upper wall part in an upper part of the water jacket and a lower wall part in a lower part of the water jacket, the upper wall part relatively closer to the inner wall surface and the lower wall part relatively closer to the outer wall surface;
• and
• an elongated contact member fixed at one end to the upper wall part of the spacer body member, changeable between a first posture separated from the outer wall surface and a second posture contacting the outer wall surface, and having a higher heat conductivity than the spacer body member and the wall of the cylinder bore,
• wherein the contact member is in the first posture in a state where coolant is not filled in the water jacket and the engine is not operated, and is in the second posture in a state where the coolant is filled in the water jacket and the engine is operated.