What was found
DIRTY SOCK/OIL OODR IN FLIGHT DECK WITH LEFT PACK OFF AND RIGHT PACK ON ODOR FADES AWAY. WITH LT PACK ON AND RT PACK OFF ODOR COMES BACK. FOUND MAINTENANCE MESSAGE 21-21191 AND 21-23401 LATCHED. LT PACK OPS FOR ABOUT 5 MINS & SHUTSDOWN DUE TO OVERTEMP. SUSPECT LT PACK OVERHEAT TO BE THE SOURCE OF REPORTED CABIN ODOR. R & R OF THE LOW LIMITER VALVE. AFTER REPLACEMENT OF THE LOW LIMITER VALVE, TEST PASSED, AND BOTH MAINTENANCE MSG SHOWS NOT ACTIVE NOR LATCHED. OPERATED PACK FOR 30 MINS WITH NO ABNORMAL ODOR NOTED. ALSO PERFORMED DETAILED INSPECTION AND OPS CHECKS FOR ODOR IN THE FLIGHT DECK & CABIN. IAW AMM 05-51-58-800-801-C3. ALL CHECKS PASSED, AIRCRAFT RETURNED TO SERVICE.