What was found
AIRCRAFT 5042, JUST BEFORE TOP, SMELL PLASTIC (BURNING) DID FUME SMOKE CHECKLIST AFTER ISOLATING CABIN FANS, GALY & CAB, VENTILATION. ODOR WENT AWAY. RESTORED VENTILATION-ODOR CAME BACK. OVRD VENTILATION WAS RESELECTED. ODOR WENT AWAY IN CKPT. CABIN STILL SMELLED FUMES BY LANDING SMELL WENT AWAY IN CABIN. FOUND GN SYS RESERVOIR DRAIN VALVE LEAKING HYD FLUID & INGESTED INTO APU INLET. REPLACED LEAKING GREEN HYD RESERVOIR DRAIN VALVE IAW AMM 29-12. (LP 8538690 - AIRCRAFT WAS GROUNDED)