What was found
ON APPROACH, LOWERED LANDING GEAR, LT MAIN GEAR SHOWED UNSAFE IN BOTH SYS 1 AND SYS 2 AND NR 3 GEAR SYS. ON GO AROUND, GEAR CAME DOWN. CREW AND STATED LIGHTS WENT SAFE AFTER GO AROUND, RAISED GEAR AND TRIED AGAIN. RECEIVED UNSAFE LIGHTS AGAIN FOR LT MLG. FOUND LT GEAR WOULD TAKE APPROX 90-120 SECONDS TO START TO EXTEND AFTER RT GEAR, THEN WOULD OPERATE NORMALLY REF TSM 32-30-00. REMOVED MLG RESTRICTOR VALVE & FOUND IT CONTAMINATED. REPLACED VALVE, REMOVED MLG DOOR RESTRICTOR VALVE, NO CONTAMINATION FOUND. REPLACED AS A PRECAUTION. PERFORMED NUMEROUS GEAR SWINGS. OPS CHECKS NORMAL. R & R GREEN SYSTEM LOW PRESSURE & HIGH PRESSURE FILTERS. FOUND SMALL AMOUNT OF PARTICLES IN GREEN SYSTEM HIGH PRESSURE BOWL. SYSTEM LEAKS CHECKS GOOD INFORMED MOCC. ACFT OK FOR SERVICE, REF MM 32-31-57-4 & 32-31-58-4.