A heat exchanger cooling system includes: a passage extending from a water tank and branching off into a first passage and a second passage at a branch portion provided in the middle of extension of the passage, the passage including a water discharge portion provided on a distal end side of the first passage so as to face a radiator; a pump configured to send water into the passage from the water tank; a first opening-closing valve provided in the first passage and configured to open and close the first passage; a second opening-closing valve provided in the second passage and configured to open and close the second passage; and a controlling portion configured to control an operation of the pump and to control opening and closing of the first opening-closing valve and the second opening-closing valve.