What was found
AFTER LEVELING AT FL230, THE FLT CREW HEARD A LOUD THUNK AND FELT A SINGLE JOLT. STRONG ODOR WAS IN THE CABIN. THE NR 2 ENGINE WAS SHUTDOWN, AN EMERGENCY WAS DECLARED AND THE FLT RETURNED TO GEG WITHOUT FURTHER INCIDENT. NR 2 PROP FEATHERED WHEN THE ALTERNATE FEATHER WAS IMPLOYED. WHEN THE NR 2 ENGINE WAS SHUTDOWN THE ODOR IN THE CABIN DISAPATED. UPON INSPECTION FOUND NR 2 CHIP ENGINE OIL TANK CHIP DETECTOR WAS COATED WITH PIECES OF METAL. IT WAS DETERMINED THAT THE ODOR IN THE CABIN WAS TURBINE OIL. TEARDOWN ANALYSIS OF ENGINE SHOWED NR 4 BEARING WAS LOOSE IN ITS HOUSING.