An engine protection system for a construction machine can individually diagnose the exhaust temperature specific to each cylinder of an engine corresponding to an engine revolution speed in order to find an abnormal condition of each engine cylinder in advance. A revolution speed sensor 14 detects revolution speed of an engine mounted in the construction machine and, a plurality, e.g., 16, cylinder temperature sensors 20a-20p detect exhaust temperatures of respective cylinders of the engine. A data recording unit 26 and a display controller 24 store the detected engine revolution speed and the detected exhaust temperatures of the respective cylinders. Trend data, which is produced based on the stored data, is sent to an office via a portable terminal and the display controller 24 outputs, a signal for playing back and displaying snapshots based on the stored data to a display unit 23 disposed in the cab 5.