What was found
ACFT DEPARTED, ENROUTE, PILOT NOTED LT ENG OIL PRESSURE FALLING, PILOT MONITORED OIL PRESSURE AND AFTER A FEW MINUTES, HE NOTED THE OIL PRESSURE WAS STILL FALLING. THE PILOT SHUT DOWN THE LT ENGINE AND DECLARED AN EMERGENCY LANDING. AFTER LANDING, MX TROUBLESHOT SQUAWK, FOUND AN O-RING THAT HAD JUST BEEN CHANGED, WAS BROKEN IN HALF. FOLLOWED THE ENG MM TO RESOLVE THE ISSURE AND RETURNED TO SERVICE.