As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
EXHAUST FUMES IN CABIN NOTICED DURING CLIMB AND AT CRUISE ALTITUDE. (FL400) SEEMED TO GET WORSE WHEN TEMPERATURE CONTROL CALLED FOR HEAT. THEN SMELL SEEMED TO DECREASE WHEN TEMPERATURE SETTING WAS REDUCED. AT LOWER ALTITUDES AND ON GROUND AFTER LANDING EVENTUALLY BECAME FAR LESS NOTICEABLE. SUPPLEMENTAL INFORMATION: REMOVED AND REPLACED COALESCERS PN: 746451-3