NHTSA Complaint #11526097 — 2016 TOYOTA PRIUS

We were driving kids to camp and the thermometer light went on. It was blinking for a while, then turned off and then turned steadily on. We weren't sure what to do, so we called our trusty mechanic who said "bring it in right now." We did and it turned out that this was a broken head gasket. Our car is regularly maintained by a trusted Prius mechanic and has less than 78K miles, despite its age. From our mechanic: We found the engine coolant was low in the radiator. We filled the system and pressure-tested, found no external leaks. The thermostat and fans operate normally. We found 54 ppm HCs in the radiator initially, and after a test-drive we re-checked and found 110 ppm HC in the radiator. Combustion chamber gas is getting into the cooling system, typically a symptom of headgasket failure. The cylinder head needs to be removed to evaluate. FYI this is the first headgasket failure we have seen on the 4th gen Prius, but it is the same engine designation as the 3rd gen Prius, which has a pattern problem of headgasket failure. The expectation is that the failure is the same, but we need to open the engine to evaluate. Given the low mileage, it might be worth pushing Toyota for a goodwill warranty even though it is out of the official powertrain warranty period. I called Toyota and they refused to pass along a goodwill warranty.