What was found
AT TOP OF DESCENT INTO BOMBAY, NR 4 ENGINE WAS SHUTDOWN DUE TO FIRE WARNING. AIRCRAFT LANDED WITHOUT INCIDENT. MAINTENANCE RESET RELAYS AND INSPECTED WIRING SYSTEM. OPS CHECKED GOOD ON GROUND. AT DEPARTURE, PROBLEM REOCCURRED, AIRCRAFT RETURNED TO BLOCK, SECURED NR 4 ENGINE LOWER FIRE LOOP AND WARNING INDICATION EXTINGUISHED. TROUBLESHOT SYSTEM AND UNABLE TO DUPLICATE PROBLEM.