What was found
(CAN) LEVELING OFF AT FL 240 AFTER TAKING OFF NR 1 ENG OIL PRESSURE WARNING LIGHT ILLUMINATED WITH ASSOCIATED BELOW 40 PSI IND. ON GAUGE. ENG SHUTDOWN&PROP FEATHERED AS PER CO POLICY, PILOT CONTACTED MOC&ELECTED TO RETURN BACK TO POINT OF DEPTR&LANDED W/O INCID..MAINT ONSITEAND WERE DISPATCHED TO INCOMING A/C UPON INIT INSP THEY DISCOVERED THAT OIL COOLER LEAKING PARTS WERE SENT FROM YHZ INST&TH E ENG GROUND CHECKED SERVICEABLE. A/C DISPATCHED BACK INTO SERVICE W/O FURTHER INCID.. ONCE OIL COOLER BACK IN YHZ IT PRESSURE TESTED WHICH REVEALED THAT WELD ON ONE OF TANKS HAD RUPTURED