As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
THE BELLOWS INSIDE THE BRADED CONNECTION CRACKED OUT LEAVING A HOLE ABOUT .75 IN IN DIA AT THE UP STREAM SIDE OF THE FLEXIBLE CONNECTOR. THE PROBLEM WAS DISCOVERED ON A MAINT RUN UP AT WHICH TIME THE FIRE DETECTION SYS WAS ACTIVATED FROM AN OVERHEAT SITUATION. RECOMMEND REMOVING THE ELBOWS AND CHECKING THE BELLOWS FOR CRACKS WITH A BORESCOPE. (K)