after reading the ad that faa issued,my impresion was that the blueing was on the bearing shaft,this is not what the thermal fuses are for (they are for an electrical overheat-ie a phase dropped out or the motor seized-fod in the impleler ????-which could be ice or spanners etc) and as such are removed from this equation
the ad also mentioned that the casing had melted in one removed pump indicating again the fault could be on the shaft on the pump motor/bearing,of course this could also be from running the pump excesivly with no load on (ie no fuel in impleller housing)
blueing on metal surfaces (that reach 1100 degs) that are rubbing will be from very localised heat