ENGINE, FUEL, 4-6. Cooling TM   10-3930-643-20 EXHAUST  AND  COOLING  TROUBLESHOOTING  AND  MAINTENANCE. System    Troubleshooting. MALFUNCTION TEST OR INSPECTION CORRECTIVE   ACTION c . ENGINE RUNS COLD. Step  2. Inspect   and   test   thermostat.   Refer   to   paragraph   4-29. Replace   if   inoperable. If   thermostat   operates   properly,   go   to   step   3. Step   3. Inspect   and   test   coolant   temperature   gage   and   sending   unit. Replace   if   faulty. Refer   to   paragraph   5-16. If   problem   continues,   notify   Direct   Support. 4-21