When to replace your thermostat
“You may find that the heater in the cabin doesn’t blow out hot air and fuel consumption will increase”
Symptoms of a thermostat stuck in the open position include the engine running cold, or at least not getting up to temperature. You may find that the heater in the cabin doesn’t blow out hot air and fuel consumption rises.
If the thermostat is stuck closed it will prevent water in the engine jacket from reaching the radiator. The engine will overheat (often quite quickly) and start running poorly. There’s a danger that the head gasket will fail, along with other seals - stop the engine immediately and replace the thermostat as soon as the engine is cool.
All cars are slightly different, so if it is time to change your thermostat, use our before-you-begin checklist, and find your car for specific instructions.