TM10-3930-660-10 b.  Engine   Gauges. Key Control   or   Indicator Function 1 2 If   the   coolant   temperature   exceeds   220°   For   the   warning   light   illuminates, shut   the   engine   down   immediately.   Do   not   operate   the   vehicle continuously  at  a  water  temperature  above  210°  F. Water   Temperature   Gauge Indicates   temperature   of   the   engine   water   and   coolant. Normal   operating   temperature   of   water/coolant   is between  180°  F  and  210°  F. If  the  oil  pressure  fluctuates,  drops,  or  if  the  warning  light  is  illuminated, stop  the  engine  and  find  the  cause.  Do  not  operate  the  engine  at  oil pressures  lower  than  10  psi. Engine   Oil   Pressure   Gauge Indicates  the  oil  pressure  of  the  engine.  Normal  oil pressure   at   operating   temperature   and   maximum governed  rpm  is  between  30  psi  and  80  psi. 2-3