What was found
CRANKCASE BREATHER TUBE MALFUNCTION. STOCK 172M BREATHER TUBE HAD SLIPPED DOWN IN CLAMPS. LOWER CLAMP COVERED 'WHISTLE HOLE'. THIS COULD RESULT IN BREATHER TUBE BLOCKAGE WITH ICE DURING FLIGHT AT LOW OUTSIDE AIR TEMPERATURE. SAME PROBLEM WAS ADDRESSED IN AD 82-07-02. (THIS AD WAS FOR MISSING WHISTLE HOLE IN STC APPROVED EQUIPMENT.) FIX WAS TO REPLACE BREATHER TUBE CLAMPS. PART TOTAL TIME: 18 YEARS, 6,000 HOURS.