What was found
CREW REPORTED DUCT SPLIT DURING CRUISE. CONSTANT SPLIT NOT A SPIKE. R=20, L=35. N1 SPEED 88 PERCENT. ALTITUDE= 37,000 FT ISOLATION VALVE= AUTO. ENGINE BLEEDS=OPEN. APU=OFF. BOTH PACKS= OPERATING. COWL AND WING ANTI ICE=OFF. CABIN PRESSURIZATION=GOOD. ACFT GROUNDED. ACCOMPLISHED HEALTH CHECK ON NR 2 ENGINE BLEED AIR SYS IAW HEALTH CHECK WC NG-36WC-00001. PRSOV FAILED WRENCH TEST, 450 DEG. SENSE LINE LEAKING, PRECOOLER CONTROL VALVE FAILED CONTROL PRESSURE REGULATION. R & R PRSOV IAW AMM 36-11-04-000-801 FOR REMOVAL AND AMM 36-11-04-400-801 FOR INSTALLATION. R & R 450 DEGREE SENSE LINE IAW TC NG36WC-00001. R & R PRECOOLER CONTROL VALVE IAW AMM 36-12-02-000-801 FOR REMOVAL AND AMM 36-12-02-400-801 FOR INSTALLATION AFTER INSTALLATION PERFORMED HEALTH CHECK ON INSTALLED PARTS IAW TC NG-36WC-00001, OPS CHECKED GOOD, ACCOMPLISHED ENGINE BLEED AIR CROSSOVER OPS CHECK- TEST IAW AMM 36-11-00-710-801. OPS CHECKED GOOD.