What was found
AFTER BOTH ENGINES STARTED AND AT IDLE THRUST RIGHT DUCT PRESSURE READ 10 PSI LEFT DUCT PRESSURE READ 15. GROUNDED - YES. ACCOMPLISHED #2 ENG BLEED AIR SYS HEALTH CK REF B737-800 AMM 36-11-00. HIGH STAGE REG FAILED TEST. REPLACED HIGH STAGE REGULATOR REF AMM 36-11-07 PB 401. ALSO FOUND CONTROL PRESS LINE BROKEN AT HIGH STAGE VALVE. REPLACED LINE. PERFORMED ENG BLEED AIR CROSS OVER TEST AMM 36-11-00. FAILS STEP 4D (8). DUCT PRESS IS 55 PSI AT 70% N1. REMOVED AND REPLACED PRSOV. ALL TEST PASSED REF AMM 36-11-04.