What was found
ON CLIMBOUT, RT WING NR 4 SPOILER WAS FLOATING CAUSING A/C TO ROLL LT AND BETA TARGET TO BE OUT TO RT. TURNED BACK AND LANDED WITHOUT FURTHER EVENT. MX PLACED NR 4 SPOILER ON MEL 27-64-01, COND 3, & DEACTIVATED BOTH LT & RT WING NR 4 SPOILERS. R & R RT WING NR 4 SPOILER SERVO CONTROL (ACTUATOR) IAW AMM 27-64-51, OPS CK GOOD. FUNCTIONAL CHECK CONFIRMED FAILURE OF SPOILER SERVO CONTROL ACTUATOR. TEARDOWN OF UNIT FOUND INSULATION OUT OF LIMITS, SEALS & PACKINGS WORN, GROOVES IN PISTON, AND RING, LOCK NUT, & TRUNNION BUSHINGS DAMAGED. REPLACED SEALS & PACKINGS IN CUP VALVE AREA OF ACTUATOR ASSY, CLEANED FILTER, REWORKED PISTON, & REPLACED RING, LOCK NUT, & TRUNNION BUSHINGS. UNIT REPAIRED & TESTED IAW CMM.