TM 10-3930-664-10 d. Gauges. KEY OR CONTROL FUNCTION CAUTION 1 Engine Oil Pressure Gauge Operates when engine is running.  Indicates pressure of engine oil.  Normal engine oil pressure is 30-60 psi (207-414 kPa). CAUTION 2 Water Temperature Gauge Operates   when   ignition   switch   is   ON.      Indicates   temperature   of   engine coolant.  Normal operating temperature for coolant is 180° - 210° F (82° - 99° C). If oil pressure drops to 15 psi (103 kPa) or lower (red zone on gauge) or the warning indicator illuminates, stop the engine and find the cause.  Do not operate the engine at oil pressure lower than 15 psi. Continuous  operation  with  low  coolant  temperature  (below  140°  F(66°  C))  or  high  coolant  temperature (above 215° F(101° C))  can  damage  the  engine.    If  the  coolant  temperature  exceeds  215°  F(101°  C)(red zone on gauge) stop the 4KRTFL, move the  travel  and  range  select  lever  to  neutral,  and  allow  engine  to operate at idle.  Check gauge to see if coolant temperature returns to normal operating range, 180° - 210° F (82° - 99° C).  If temperature does not return to normal operating range within five minutes, stop the engine and find the cause. 2-7