What was found
FOLLOW-UP TO RECENT HISTORY OF DUCT PRESSURE SPLIT WITH LT PRESSURE LOW. ACFT GROUNDED. ACCOMPLISHED TC NG-36WC-00001, NR 1 ENG BLEED AIR HEALTH CHECK, NO DEFECTS NOTED. REPLACED PRECOOLER VALVE REF MM 36-12-02-400-801. REPLACED 390 DEGREE SENSOR REF MM 36-12-03/401. ACCOMPLISHED ENGINE BLEED CROSSOVER TEST, DURING HIGH POWER RUN AFTER 1MIN AND 30 SEC, LT DUCT PRESS. DROPPED TO L-15, PSI R-42. REF MM 36-11-00-710-801. FOUND HIGH STAGE VALVE INTERMITTENTLY NOT COMPLETELY CLOSING. REPLACED NR 1 ENGINE HIGH STAGE VALVE REF MM 36-11-07-401. PERFORMED BLEED CROSSOVER CHECK. NO HELP, CONDITION STILL EXISTS. REPLACED LT 4505 THERMOSTAT IAW 36-11-05-400. OPS & LEAK CK GOOD. FOUND HIGH STAGE VALVE REG SENSE LINE 16135-81 PN LEAKING. REPLACED LINE, LEAK CK GOOD. ACCOMPLISH ENGINE BLEED AIR CROSSOVER, OPS TEST IAW 36-11-00-710-801. OPS CK GOOD.