TM10-3930-660-10 3-8. AIR   CLEANER   -   SERVICE   (Cont.) e.  Install  the  outer  cover  and  clamp.  Tighten the   thumbscrew. f.  Check  the  rubber  evacuator  valve  to  be sure  it  is  not  plugged  or  damaged. g.   Reset   the   air   intake   restriction   indicator by  pressing  button  on  end  of  indicator. 3-9. RADIATOR  -  SERVICE This   task   covers: Checking  radiator  coolant  level  and  adding  coolant  as  necessary. 1. 2. CHECK   COOLANT   LEVEL   IN   OVERFLOW BOTTLE.   BOTTLE   MUST   BE   1/3   TO   2/3 FULL. NOTE Use  a  50-50  mix  of  ethylene  glycol (MIL-A-46153B)   and   clean   water   for coolant.   Plain   water   is   not   recommended. Make   coolant   mixture   before   adding   ethy- lene  glycol  and  water  to  the  coolant  bottle. ADD   COOLANT   TO   OVERFLOW   BOTTLE. a.  If  bottle  is  less  than  1/3  full,  add approximately   one   quart. The   cooling   system   operates   under   pressure which  is  controlled  by  a  radiator  cap.  It  is dangerous  to  remove  the  cap  while  the  system  is hot  because  hot  steaming  gases  will  escape  and burn  you.  Always  turn  the  cap  to  the  first  stop and  allow  the  pressure  to  escape  before removing   the   cap   completely. b.  If  no  coolant  is  visible  in  the  bottle,  add  2 quarts  of  coolant  to  bottle  and  fill  radiator with    coolant. 3-12