As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING CLIMB FL 180 PRESSURIZATION LT DUCT PRESSURE 15 R 41 N1'S 97.5 PERCENT. IN CRUISE 88 PERCENT N1 FL 380' L 40, R 40. IN DESCENT 35 PERCENT N1 FL240, L21, R22. GROUNDED YES. ACCOMPLISHED T/C NG 36WC 00001 ON NR 1 ENGINE NO DEFECTS NOTED. REPLACED NR1 PRECOOLER CONTROL VALVE REF 36-12-02, OP'S & LEAK CHECK GOOD. ACCOMPLISHED "REPAIR CONFIRMATION" TASK OF FIM 36-10-00-810-807 CK'D GOOD. RAN ENGINES TO 80 PERCENT N1 MAINTAINED BLEED SCHEDULE WITH "NO SPLIT".