TC reported air discharge sound heard from driving cab. MR pressure drop to 8.8 bar when train at pl atform. MR charge to 10 bar when moving. ~~~~~ #3685 Check and found air leak from wiper engine. Replaced wiper engine and function check ok. ER downloaded PTU0006. Wiper engine -Old s/n: 307. New s/n: 156. Not: 2167300 raised to RSW. Found air compressor charging rate failed. Done by Jack/Sateesh/Koh. #3686 found Air dryer heavy leak when compressor running. Replaced air dryer and function check ok. #3686 compressor Cut in-8.3 bar. Cut out-10.3 bar. Charging time-2 min 5sec. Air leak test-0.2 bar/5min. Air Dryer- Old s/n: 3515480326. New s/n: 3515280296. Not: 2167420 raised to RSW. Done by Jack/Sateesh/Koh. 07/06/20.