What was found
AFTER TURNING ON B-PUMP AILERON SYSTEM B FAILURE LIGHT REMAINED ILLUMINATED 3000PSI NOTED FOR B SYSTEM WITH AILERONS VERY DIFFICULT TO MOVECLEANED OXIDATION FROM AILERON B SYSTEM SOV AND FROM AIL PRESSURE SWITCH. MANUALLY CYCLED SOV AND IT WOULD DRIVE BACK TO CLOSED.INSPECTED AILERON B SYSTEM LIMIT SWITCH FOR LOOSE WIRE, NONE FOUND,CYCLED B SYSTEM. DURING TAXI THE B SYSTEM AILERON LIGHT ILLUMINATED ON 2 OCCASIONS. EACH FOR 15 TO 20 SECONDS. EACH TIME THE B SYSTEM AILERON SWITCH WAS CYCLED AND THE PROBLEM CLEARED. REMOVED AND REPLACED B SYS AILERON CONTROL VALVE IAW B727-200 MM 27-10-142, OPS CHECK GOOD REMOVED AND REPLACED PLUG D128 ON SYS B AILERON SHUT-OFF VALVE.