What was found
DURING ROTATION, NR 4 BRAKE TEMP CLIMBED TO 800 DEGREES C WITH AN ASSOCIATED ECAM FOR HOT BRAKES. SELECTED GEAR DOWN AND BRAKE COOLED TO BELOW 500 DEGREES C ON ECAM AND RETURNED TO DEPARTURE AS A PRECAUTION. A NORMAL CONFIGURATION, OVERWEIGHT LANDING PERFORMED. MX NOTED THAT NR 4 BRAKE WAS COLD TO THE TOUCH. RELEASED FOR SERVICE. THE ACFT FLEW ITS NEST 2 LEGS WITHOUT INCIDENT. DURING TROUBLESHOOTING, REVEALED A FAULTY BTMU. REPLACED.