What was found
ABOUT TO DEPART BFM. TURNED ON APU BLEED. CURRIER AREA FILLED WITH SMOKE. TURNED OFF APU BLEED AND DEPARTED AC. FOUND OIL PUMP NUT LOOSE AT OIL COOLER INLET, TIGHTEN AS REQUIRE IAW A300-600 AMM CH 49-91-16-4 AND SERVICE APU OIL IAW AMM 12-13-49-00. REMOVED AND REPLACED #1 AND #2 PACK WATER SEPARATOR COALESCER IAW AMM 21-51-16-03,RAN APU FOR 1 HOUR IAW AMM 49-00-00-05 GRND OPS AND LEAK CK GOOD A/C RETURN TO SERVICE.