What was found
AFTER APU ON SPEED FOR OVER 2 MINUTES, TURNED ON ECS TO APU. BLUISH-GRAY SMOKE BOILED OUT OF THE COCKPIT AIR VENTS, HEAVIER OUT OF THE COPILOTS SIDE. NO SMOKE NOTED IN CABIN. REMOVED APU PN 3800710-1 SN P-187 IAW CMP 490001. INSTALLED ON NEW APU IAW MM 49-10-00. SERVICED APU WITH 254 OIL IAW 36-150 IAW MM CHAPTER 49-20-00. PERFORMED APU OPERATIONAL TEST, ALL TEST PASSED. LEAK CHECKED GOOD. NEW APU CLEARED SMOKE DISCREPANCY. WORK PERFORMED IAW CMP 539701 & 36-150 MM CHAPTER 49-20-00.