As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
THE ENGINE WAS DISASSEMBLED TO DETERMINE THE REASON FOR THE REPORTED PROBLEMS. DISASSEMBLY OF THE OIL PUMP ASSEMBLY REVEALED THE POST SB 7185 PLATE HAD BECOME WELDED TO THE SCAVENGE ELEMENT CAUSING IT TO SHEAR THE SHAFT DRIVE PIN. THIS FAILURE CAUSED FLOODING OF THE NR 4 BEARING CAVITY, ULTIMATELY RESULTING IN AN OIL FIRE AT THE NR 4 BEARING AREA.