As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
SHIP 3776 -ATB- RETURNED TO JFK DUE TO SMELL THROUGHOUT THE CABIN ALONG WITH ASSOCIATED GRINDING NOISE THAT FOLLOWS THROTTLES. CORRECTIVE ACTION: FOUND LT ACM FROZEN. REPLACED SAME. FOUND PRIMARY HEAT EXCHANGER CRACKED. REPLACED SAME. DUE TO ACM DAMAGE SUSPECT POSSIBLE ICING. REPLACED STANDBY TEMP CONTROL VALVE, RE-HEATER, INSPECTED DRAIN LINES AND CLEARED INLET WATER NOZZLE. ALL OPS CHECKS OK. AIRCRAFT RETURNED TO SERVICE.