What was found
ON TAXI OUT, THE BRAKES GRABBED AND STOPPED THE AIRCRAFT. BRAKES AUTO BRK FAULT OCCURRED. RECYCLED THE A/SKID AND N/W STRG SWITCH OFF/ON, PER THE QRH AND ATL MX. CONTINUED SHORTLY AFTER RE-TAXIING, IN A TURN HAD NO BRAKE RESPONSE TO PILOT INPUT AND THE FAULT RE-OCCURRED. THE BRAKES SELF ENGAGED AND THE AIRCRAFT STOPPED, SUBSEQUENTLY TOWED TO THE GATE. CORRECTIVE ACTION: T/S PER A330 TSM 32-42. FAULTS NORMAL BRAKE SELECTOR VALVE REMOVED AND REPLACED NORMAL BRAKE SELECTOR VALVE 4GG, PER AMM 32-42. REMOVED BOTH ACCUM 5426G AND 5427GG, PER A330 AMM 32-44. INSTALLED AND SERVICED BOTH BRAKE ACCUMULATORS, PER A330 AMM 32-44. BLEED AND SERVICED THE ALT BRAKES MASTER CYLINDER RESERVOIR, PER A330 ALL 32-43. R & R RT COCKPIT ALT BRAKE MASTER CYLINDER, PER A330 AMM 32-43. R & R ALTN BRAKE MANIFOLD TRANSDUCER 3GK2, PER A330 AMM 32-44. REPLACED ALTERNATE BRAKE DUAL VALVE, PER A330 AMM 32-43, BLED ALT HYD SYSTEM, PER A330 AMM 32-43. ALT SYSTEM CHECKS OK, PRESSURIZED PARKING BRAKE ACCUMS, REF A330 AMM 12-14. LEAK CHECKS GOOD. RESET SAFETY VALVES, PER A330 AMM 32-42. BLED BRAKE SYSTEM, PER A330 AMM 32-42. NML AND AUX BRAKES CK OK.