What was found
SHORTLY AFTER T/O IN CLB POWER LEFT DUCT PRESSURE FLUCTUATING BETWEEN 30-35, RT 50 PSI. AS WE CONTINUED TO CLIMB LEFT SIDE FLUCTUATED LESS AND LESS UNTIL CRUISE RT DID NO FLUCTUATE AT ALL BUT STILL HAD A SPLIT LEFT 38 PSI, RT 45 PSI. GROUNDED - YES. DUCT SPLIT WITHIN DEFERRABLE LIMITS REF B737-800 FIM 36-10 TASK 811. CREATED A PLT DEFERRAL FOR 7 DAYS TO PERFORM FURTHER TROUBLESHOOTING. ACCOMPLISHED T/C NG-36WC-0001 UP TO STEP 6 ACCOMPLISHED OPERATION TEST NO DEFECTS NOTED. COMPLETED STEP 6 OF TASK CARD NG-36WC-00001 FOR #1 ENGINE. 35/40 DUCT PRESSURE FLUCTUATION NOTED AT 80% N1. REMOVED & REPLACED #1 ENGINE BAR PER B737-800 AMM 36-11-03-000/400-801. ACCOMPLISHED BLEED AIR OPS TEST IAW AMM 36-11-00-710-801. #1 ENGINE SATISFIES FIM 36-10 TASK 807 GROUND VERIFICATION REPAIR CONFIRMATION CRITERIA.