Staff(CBR) unusual sound heard from undercarriage. Staff(KTB and YCK) checked and confirmed unusual hissing sound coming from car 1624. MR pressure is 10.5 bar.Train withdrew back to BSD. ~~~~~ Staff(CBR) unusual sound heard from unde     Check and confirm hissing sound from #3624 cab underframe WFL joint burst and cause heavy air leaking. Replaced WFL joint and function test ok.Air leak test 0.4bar/5min. Done by Faddzal/Sanip.  28/06/21