What was found
NUMBER 4 ENGINE OIL SYS STATUS MESSAGE, PRECAUTIONARY SHUTDOWN OF NR 4 ENG PER QRH. M12 - DURING A/C BACK TO GATE W/ REGARDS TO ENG NR 4 OIL SYS STATUS MSG FOUND OIL CAP NOT INSTALLED PROPERLY. (PERFORMED PRECAUTIONARY INSPECTION OF NR 4 ENG FUEL OIL HEAT EXCHANGER, FOUND OIL SUPPLY LINE CRACKED. REMOVED AND REPLACED OIL SUPPLY LINE, LEAK CHECK GOOD PER AMM 79-21-01. PERFORMED ENGINE RUN IAW B747 AMM 71-00-00. ENGINE OPERATION NORMAL. PERFORMED ENGINE WIND MILLING INSPECTION IAW B747 AMM 71-00-00-200-806-G00. NO DEFECTS NOTED. LP 1488143 - M12: CHECKED OIL CAP, NO ABNORMALITIES. SECURED OIL CAP AND CHECKED OK PER AMM 12-13-03/301.)