What was found
FLIGHT 858 DEPARTED MAR AND DURING THE CLIMB THE CREW REPORTED THE NR 1 ENGINE LOW OIL FILTER BYPASS LIGHT ILLUMINATED, THE CREW ACCOMPLISHED COMPANY ALTERNATE PROCEDURES, THE NR 1 ENGINE WAS SHUT DOWN AS A PRECAUTIONARY. THE AIRCRAFT RETURNED TO MAR WITHOUT ANY FURTHER INCIDENT, MAINTENANCE TROUBLESHOT THE PROBLEM AND FOUND THE NR 1 ENGINE MAIN OIL FILTER CONTAMINATED. THE MAIN OIL FILTER WAS REMOVED AND REPLACED, THE NR 1 ENGINE OIL BYPASS SWITCH WAS REMOVED AND REPLACED, THE NR 1 ENGINE WAS RUN TO TAKEOFF POWER FOR 5 MINS AND A LEAK CHECK, AND AN OPERATIONAL CHECK, ALL CHECKED GOOD, ALL WORK ACCOMPLISHED IAW P&W MM CH 72-00-00, & B-727 MM CH 79-33-01, P&W MM CH 72-61-00, P&W MM CH 71-00. THE AIRCRAFT WAS