As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ICE BUILDUP ON VENT TUBE CAUSED CRANKCASE PRESSURES TO INCREASE AND CRANKSHAFT SEAL TO PUSH ON RETAINERS TILL FAILURE. FLIGHT WAS AT NIGHT AND LEAK WAS NOT NOTICED TILL AFTER ACFT LANDED. THE ENGINE LOST 7 QUARTS OF OIL OF ITS 12 QUART OIL CAPACITY.