What was found
DURING CLIMB DUCT PRESSURE READ 43 PSI (R) & 20PSI (L). N1 100.2 / 100.2 N2 97.2 / 97.2. AT CRUISE DUCT PSI WAS 40 / 34. N1 88.6 / 88.6 N2 92.1 / 92.1. DESCENT 18 / 18 N1 41.2 / 40.8 N2 75.1 / 75.1. MATCHED DURING TAXI IN. DID NOT NOTICE ANY PRESSURE PROBLEMS OR ANOMALIES AT ANY TIME. REPLACED PRECOOLER CONTROL VALVE SENSOR ON NR 1 ENGINE IAW AMM 36-12-03. LEAK CHECKED GOOD NO OTHER DEFECTS NOTED. VERIFICATION FLIGHT UNSATISFACTORY. PERF. NR 1 ENG BLEED AIR SYS HEALTH CHECK. FOUND PRECOOLER CONTROL VALVE FAILING. REPLACED PCCV REF MM 36-12-02. PERFORMED SECOND BLEED AIR SYS HEALTH CHECK ON PCCV REF MM 36-11-00. VALVE CHECK PASS. PERFORMED ENG BLEED AIR CROSS OVER OPS TEST ON NR 1 ENG. PSI WITHIN RANGE REF MM 36-11-00-710-801. COMPLETED NR 1 ENG BLEED AIR HEALTH CHECK. NR 1 ENG HIGH STAGE REGULATOR FAILED OVERPRESSURE FUNCTION. REPLACED NR 1 ENG HSR PER MM 36-11-07-000-801 OPS CHECKED GOOD. WHILE PERFORMING T/C NG 36WC-00001 STEP 02 N BLEED AIR REGULATOR FAILED STEP N.(4). REPLACED NR 2 ENGINE BLEED AIR REGULATOR REF MM 36-11-03-400-801.