TM 10-3930-659-10 2-29.  OPERATE IN EXTREME COLD (Con’t). (7) Stow extension cord in compartment under driver’s seat. (8) Start engine (see paragraph 2-11). 2-30.  OPERATE IN EXTREME HEAT. NOTE When operating under desert conditions, also refer to paragraph 2-33. a.  General Guidelines. (1)  Preventive  maintenance  is  critical  when  operating  at  high  temperatures.  Forklift  truck  systems  must  be  kept cool, clean, and in good condition. (2) Check engine oil level (see paragraph 3-6), transmission oil level (see paragraph 3-7), and coolant level (see paragraph  3-8)  frequently.    Fluids  evaporate  or  break  down  more  quickly  and  seals  are  more  likely  to  leak under extreme heat. (3)  Use  correct  fluids  and  lubricating  oils  for  high  temperature  (see  LO  10-  3930-659-12).    Ensure  that  only  an antifreeze and potable water mixture is used in cooling systems. (4) Do not overfill when adding fluids.  Find and use fill marks.  Try to service fluids when outside temperature is at midpoint of temperature range for the day.  This helps avoid fluid overflows, explosions, or low levels due to expansion and contraction during hottest part of day or coolest part or night. (5) Keep radiator clean and free of dirt or debris.  Ensure that radiator fill cap is the correct pressure for the forklift truck and that it works correctly. (6) Keep transmission oil cooler screen free of dirt and debris. (7)  Check  often  for  any  wetness  or  signs  of  leaks  at  cooling  system  lines,  hoses,  seals,  seams,  drain  plugs,  or hose connections.  Ensure that hoses are not spongy or brittle, and check fan belts for cracks or breaks. (8) High temperatures can expand belts; have belts adjusted as necessary. (9) In hot climates with relatively high dew levels and high humidity, overnight condensation can affect fuel tank, fuel lines, and hydraulic system reservoir.  Have Unit Maintenance drain fuel filter at least once weekly, and check hydraulic oil level sight gage for foamy oil appearance both morning and night. (10)  Heat  and  sun  cause  more  rapid  deterioration  of  rubber,  plastics,  and  other  materials.    Check  tires  more frequently  for  damage  or  wear.    Visually  check  tires  for  proper  inflation  and  have  Unit  Maintenance  add  air when tires are cold and at midpoint of temperature range for the day. 2-71