TM   3930-638-24&P 12-11.   EXHAUST   SYSTEM   TROUBLESHOOTING   (cont) MALFUNCTION TEST  OR  INSPECTION CORRECTIVE ACTION 2. EXCESSIVE EXHAUST SMOKE Check  if  muffler  requires  cleaning. Clean  (para  2-16). NOTE If problem is not corrected, notify direct support maintenance. 12-12.   COOLING   SYSTEM   TROUBLESHOOTING MALFUNCTION TEST  OR  INSPECTION CORRECTIVE ACTION 1. ENGINE  OVERHEATS Step 1. Check fan belt for proper tension. Depress fan belt midway between fan pulley and crankshaft pulley. Fan belt should be deflected approximately 1/2 inch. a. If fan belt does not deflect 1/2 inch approximately, adjust it (para 2-17f) b. If fan belt deflects 1/2 inch approximately, proceed to step 2 below. Step  2. Inspect fan belt for damage, wear, oil covered, or riding deeply in pulley groove. a. If any of the above conditions are observed, replace fan belt (para 2-17f). b. If none of the above conditions are observed, proceed to step 3 below Step 3. With engine idling, remove radiator cap and observe coolant to see if it moves indicating water pump is operating. a. If coolant movement is not observed, replace water pump (para 2-17e). b. If coolant movement is observed. proceed to step 4 below. Step 4. Check radiator and hoses for leakage or damage. a. If radiator and/or hoses are leaking or damaged, replace (para 2-17C and 2-17b, respectively). b. If radiator and hoses are okay, proceed to step 5 below. Step 5. Check fan blade assembly for damage. a. If fan blade assembly is damaged, replace (para 2-17 f). b. If fan blade assembly checks okay, proceed to step 6 below. 2-25