There are four main reasons your car’s thermostat might fail:
1. Overheating: The thermostat detects the heat of the engine, and uses the heat to open and close a valve. The components within a thermostat are only designed to handle operating temperatures, so when the temperature climbs too high, it’ll cause the thermostat to fail.
2. Contaminated coolant: Sludge can build up in coolant, and can get inside the thermostat. This can restrict the efficacy of flow, or prevent coolant flowing through the thermostat. This means the thermostat won’t get an accurate reading, and can lead to your engine overheating or overcooling.
3. Manufactury defects: Like most other car parts, thermostats are mass produced in factories. Sometimes, thermostats slip through the inspection stage with minor defects which can lead to thermostat failure.
4. Time: Thermostats are constantly being heated and cooled, and after a while, the internal components wear out. It’s a slow process, but the temperature at which the thermostat will open climbs higher and higher, until one day your engine overheats.
To prevent the above problems from occurring, get your cooling system checked by a professional technician.