Pax feedback to staff (ADM) Rear DT caremit loud sound. Staff (ADM) checked and confirmed no abnorm alities in between ADM2 to SBW2. Staff (YIS) onboard train c hecked and confirmed when train departing, there was an air ~~~~~ Pax feedback to staff (ADM) Rear DT-3712  car emit loud sound. Staff(ADM) checked and confirmed no abnormalities in between ADM2 to SBW2.Staff (YIS) onboard train checked and confirmed when train departing,there was an air discharge sound emitting from the under carriage but no abnormalities. TC feedback performance and MR was normal. Train SC ce unable to board.  3712 Found air compressor safety valve keep blowing at 8 bar. Drain and check MR tank no sign of water. Check MR cock DT/M1 ok. Check filter element ok. Check air dryer wiring ok, No sign of looseness. Install new safety valve to no avail. reinstal back the original safety valve. When aux in observe air dryer having changeover few time and will stop at 6 bar. When air dryer change over , MR at 8 bar, Air compressor safety valve keep blowing. Suspect air dryer faulty, Replace Air dryer functional check ok, Changeover 2 min ok. No Occurance of air compressor safety valve blOW. Done by Sani/Asruddin/Haslan 44907 3712 air dryer old:3518220634 new:3515020253 notic csc:2444041