During DT-Found EMU519/520 having air le ~~~~~ TO FOLLOW-UP RECTIFICATION.  3519 A/s WFL actuator replaced & function check - OK.  Chan SW/Hanafi 44062 3519 During DT - Found having air leak noise undercarriage.  3519 A/s WFL actuator found air leak. Awaiting spare. OPS 20 raised to follow-up.  Ridzuan 44061