NHTSA Complaint #11128262 — 2011 HYUNDAI SONATA

THE THERMOSTAT HOUSING IS PLASTIC MOLDED OVER A STEEL (METAL) CORE. WHERE THE HOUSING IS BOLTED TO THE ENGINE OVER THE INPUT AND OUTPUT COOLANT ORIFICES AN INTERNAL PIECE OF PLASTIC FLAKED OFF THE STEEL CORE BEHIND THE GASKET SURROUNDING THE INPUT ORIFICE. AT REST NO COOLANT LEAKED OUT OF THE COOLING SYSTEM. HOWEVER, AT OPERATING TEMPERATURE AND PRESSURE, THE COOLANT SPRAYED OUT OF THE ENGINE IN A FINE MIST/SPRAY. ALTHOUGH THERE WAS AN ODOR OF COOLANT WHILE DRIVING, ALL SEARCHES AROUND THE HEATER CORE, UNDER VEHICLE RESULTED IN NO EVIDENCE OF COOLANT LEAK. ON AN EXTENDED TRIP AT 103,000 MILES ENOUGH COOLANT EVACUATED THE COOLING SYSTEM TO FACILITATE A BLOWN HEAD GASKET. YET THERE WERE NO WARNING LIGHTS INDICATING OVERHEATING. THE BLOWN GASKET WAS DISCOVERED WHEN THERE WAS A SOUND OF GURGLING LIQUIDS ORIGINATING FROM THE COOLANT RESERVOIR WHEN WE REACHED OUR DESTINATION, A THICK SLUDGE OF COOLANT AND OIL PERMEATED THROUGHOUT THE ENGINE, HEATER CORE, THROTTLE BODY AND RADIATOR. IT WAS DURING REPAIRS THE THERMOSTAT HOUSING WAS FOUND TO HAVE THE INTERIOR DAMAGE. IF WE HAD BEEN DRIVING 30 MILES FURTHER THAN WE DID, THE ENGINE WOULD HAVE SEIZED AT HIGHWAY SPEED, UNDOUBTEDLY CAUSING AN ACCIDENT. THANK GOD WE STOPPED WHEN WE DID.