As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ON FLIGHT 3992 DURING CRUISE CREW ADVISES THAT THERE IS A BURNING RUBBER OIL ODOR IN THE CABIN. WHEN ON THE GROUND THE TEMPERATURE STABILIZED. ACFT REMOVED FROM SERVICE. C/A R&R NR 2 ENGINE PRECOOLER. OPS CHECK GOOD. ACFT RETURNED TO SERVICE.