What was found
STL - DIVERSION - FLT 0126 - EN ROUTE FROM PHX TO MKE, NR 2 ENGINE COWL ANTI-ICE VALVE FAILED TO OPEN, DUE TO ICING CONDITIONS DIVERTED TO STL. MAINTENANCE AT STL COMPLIED WITH MEL PROCEDURE 30-3, COND 4, OPENING OF THE NR 2 ENGINE COWL ANTI-ICE VALVE. WHEN AIRCRAFT ARRIVED IN PHX, MAINTENANCE REMOVED AND REPLACED THE NR 2 ENGINE COWL ANTI-ICE VALVE IAW BMM 30-21-11 PG 401-404, OPERATIONAL CHECK WAS GOOD. VENDOR BENCH TEST OF ENGINE COWL ANTI-ICE VALVE S/N 1547AB CONFIRMED FAILURE OF UNIT. VALVE WAS FOUND TO STICK IN THE CLOSED POSITION, REGULATOR VALVE STICKS IN MID POSITION 0 PSI TO 790 PSI AFTER BEING MANUALLY CYCLED, AND FAILED BONDING TEST. REPLACED PISTON SEALS, O-RINGS, AND BEARINGS PER CMM 30-21-01.