As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FUMES IN COCKPIT ON DECENT. NO FUMES NOTED IN THE CABIN. PERFORMED HIGH POWER ENGINE RUNS WITH BOTH PACKS RUNNING. RUBBERY SMELL WAS ONLY NOTED DURING ENGINE 1 RUN UP. SMELL ONLY IN COCKPIT NOT IN CABIN. FOUND LH PACK HEAT EXCHANGER CRACKED. REMOVED AND REPLACED LH HEAT EXCHANGER. INSPECTED POWER LEADS TO W/S HEAT CONTROLLERS. NO DEFECTS NOTED. OPE CHECK SAT OF LH PACK HEAT EXCHANGER. NO DEFECTS NOTED AT THIS TIME. (THE FLIGHT DECK DONNED OXYGEN MASKS. THE CABIN DID NOT HAVE OXYGEN MASKS DEPLOYED)