What was found
DURING CRUISE AT FL410 HAD EMER BRK LO PRESS YELLOW CAS MESSAGE. ACCUMULATOR PRESSURE BLED DOWN SLOWLY FROM 1600 PSI UNTIL APROX 1100 PSI THEN DROPPED TO 100 PSI & STAYED FOR THE REMAINDER OF FLT. ACCOMPLISHED QRH & LANDED NORMAL, NO ISSUES. AFTER TOUCHDOWN, NOTICED EMER BRAKE ACCUMULATOR PRESSURE RETURNED TO 3000 PSI. PERFORMED FIM 4885 FAULT ISOLATION SUBTASK 810-013-A, OPS CHECK OF EMERG/PARKING BRAKE HYD SHUTOFF VALVE AMM 32-43-11-710-801-A/500, SYS FAILED OP CHECK, REPLACED HYD SHUTOFF VALVE IAW AMM 32-43-11 , PERFORMED NORMAL & EMER/PARKING BRAKE SYS BLEED IAW 32-40-00, MAIN HYD BLEED. COMPLETED MAIN SYS HYD BLEED, NO AIR OR DEFECTS. COMPLETED EMER/PARKING-BRAKE HYD LINE SHUTOFF VALVE OPS CHECK, NO D