What was found
IN CLIMB, THRU FL 300, LT DUCT PRESSURE 20 PSI, RT 47 PSI IN CRUSE AT FL 350, LT 22 PSI, RT 31 PSI BOTH PACKS IN AUTO AND ANTI-ICE OFF. ACFT GROUNDED. PERFORMED T/C NG-36WC-00001 "ENGINE BLEED AIR SYS HEALTH CHECK" ON NR 1 ENGINE. PRE-COOLER CONTROL VALVE FAILED, VALVE IS STILL CLOSED AT 3PSI PC, SHOULD BE OPEN. REPLACED VALVE, OPS/LEAK CHECK OK. REF MM 36-12-00. BLEED AIR REGULATOR FAILED, PC IS 19PSI, SHOULD BE 20-28 PSI. REPLACED REGULATOR, OPS/LEAK CHECK OK, REF MM 36-11-03. PERFORMED ENGINE BLEED AIR CROSSOVER OPS TEST, PASSED TEST. LT AND RT DUCT PRESSURES 41PSI-44PSI DURING REGULATED 5TH STAGE, 60 PERCENT-80 PERCENT N1, REF MM 36-11-00-710-801.