As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ROTOR TACHOMETER GEN SEAL LEAKS INTO OIL COOLER BLOWER INLET, AIR/OIL MIX TURE GETS DISTRIBUTED OVER HOT 250C20R ENGINE. REMAINDER OF AIR OIL MIXTURE ENTERS HEATER DUCTS. WHEN PILOT SELECTS HEATER, HAZARDOUS AIR/OIL MIXTURE FILLS COCKPIT. THIS PAD SHOULD HAVE A SCUPPER DRAIN LINE OVERBOARD LIKE THE 2 OTHER SEALS IN SAME PROXIMITY.