121 Operation here. Recently we had a line aircraft with a supposedly "erroneous" overtemp (fire) sensor going off on the ground on one engine." Common with a heavy tail wind, but not expected during normal ops. The sensor is there, but installed for a previous system that is now removed. Prop brake. Anyway, people ignored it until is sounded the red bells on my takeoff one day so we aborted. Our mx wanted us to MEL the system and depart with that bell going off, and we requested a mechanic look at it. Mechanic found a large problem in there, a pipe that was suppose to vent very hot engine air out the side of the cowling, was disconnected. So I am guess we were fairly lucky that the events took place as they did. I later found out that he warning system was inhibited in the air. No other engine or system indications presented.