As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PILOT REPORTED SMOKE IN THE COCKPIT, COMING FROM THE DEFROST VENT. INSPECTED UNDER PANEL WIRING FOR EVIDENCE OF HOT WIRES. NONE FOUND. INSPECTED ENGINE COMPARTMENT FOR ANY INDICATIONS OF BURNING WIRING OR ANY OTHER PROBLEM. FOUND NR 4 VALVE COVER LEAKING ONTO HEAT MUFF. REPLACED VALVE COVER GASKET.