TIMS showed Smoke External at car 1526.SM (YIS) checked and confirmed no sign of smoke or heat at rear M1 car. Rear T430 did line clear feedback no abnormalit ies. ~~~~~ 1526 TIMS showed Smoke External. SM (YIS) confirmed no sign of smoke or heat at rear M1 car. Rear T430 did line clear feedback no abnormalities.  1526 Checked external unit - OK. 1526 Checked rubber gasket - OK. Checked rubber galnd - OK. Cleaned external smoke unit. Swapped 1526 SDR11 with 2526 for monitoring. Chan SW/Aliff/Redzwan 45184