What was found
DUCT PRESSURE SPLIT IN CLIMB EXCEDED 20 PSI -CLIMB/CRUISE. FL 350 N1-101.9, DUCT PRESS L- 28, R-47. FL 390 N1-99.6, DUCT PRESS L-26, R-47. FL 400 N1-99.1, DUCT PRESS L-26, R-47. FL 400 N1-87.6, DUCT PRESS L-30, R-35. ACFT GROUNDED. PERFORMED T/C NG-36WC-00001 BLEED AIR SYS HEALTH CK ON NR 1 ENG PRECOOLER VALVE AND BLEED AIR REGULATOR FAILED. R & R PRECOOLER VALVE IAW AMM 36-12-02. R & R BLEED AIR REGULATOR IAW AMM 36-11-03. WHILE PERFORMING OPS & LEAK CHECKED, FOUND PRSOV DIAPHRAM LEAKING. R & R PRSOV IAW AMM 36-11-04 1. PERFORMED ENGINE RUN IAW AMM 36-10-00. OPS CK GOOD NO DUCT SPLIT.