5 Symptoms of a Bad Thermostat
If your home is too cold or too hot, you probably adjust the thermostat to change the room temperature. Your engine block may also get too hot or too cold, requiring a thermostat to control the engine temperature.
How does a thermostat work? Unlike home thermostats, most car thermostats don’t require electricity. Thermostats contain a wax element that blocks the flow of coolant. As the wax melts, it expands, opening a valve in the thermostat to allow coolant to flow from the radiator to the engine block.
At rest, the coolant in the radiator is at approximately the same temperature as the surrounding air. As it circulates through the radiator, it absorbs heat from the engine.
When the engine temperature drops, the coolant temperature is close enough to the ambient temperature that the wax cools and hardens again, causing the thermostat to close again. This cycle repeats to keep the engine within a certain temperature range.
Thermostats come in various temperature ranges depending on the engine and application. A 180° thermostat begins to open when the temperature of the coolant in the engine block exceeds 180°F within 3 degrees. The thermostat opens fully when the engine coolant is 15 to 20 degrees above 180°F.
When purchasing a new thermostat, be sure to select it according to the OEM specifications for your vehicle. Different engines run best at different operating temperatures.
Symptoms of a Failed Thermostat
1) Overheating
The most obvious symptom of a bad thermostat is your vehicle overheating. If the thermostat stays closed, coolant can’t circulate. This causes hot coolant to get stuck in the radiator, preventing fresh coolant from cooling the engine.
2) Reduced Engine Performance
When your engine is cold, it doesn’t run as efficiently as it does at operating temperature. Engines are built with certain tolerances designed to operate within a certain temperature range. If the thermostat is stuck open, the coolant temperature will continue to drop as it flows through the radiator, even if the engine temperature is below the operating temperature.
Operating temperature is the temperature at which the engine will burn optimally. When metals in the engine heat up, they expand. This fills up some of the empty space between the piston and the cylinder wall, strengthening the seal in the combustion chamber. Better seals mean your engine can produce more compression and be more efficient.
A car that runs too rich will burn more fuel and cause excess carbon buildup over time. Spark plugs may also become fouled. High fuel consumption also increases vehicle emissions, further straining the environment.
3) Temperature reading stays cold
If your thermostat is stuck in the open position, your car may never reach operating temperature. This is especially true on cold winter days when engine heat dissipates quickly.
4) Heating doesn’t work
Heat inside your car is generated by the heater core. The heater core is very similar to the radiator at the front of your car and works on the same principle. Coolant flows from side to side in the heater core, heating the core. As air flows over this warm core, it heats it up.
Depending on how the thermostat failed and where the heater core is in relation to the thermostat, a failed thermostat can cause the heater core to become cold. If the thermostat fails open, the cabin may take an abnormally long time to warm up. You may also notice that the heat from the vents fluctuates, going from hot to cold and back to hot again, even without changing the A/C temperature setting. These symptoms can also occur if there is air bubbling in the heater core.
5) Burnt Radiator Hose
As temperatures rise inside the engine block, so does the pressure. If the engine gets too hot, some rubber parts may start to leak or even burst.
This is very dangerous because the pressurized coolant is very hot and can easily splash into your eyes, face, or hands, causing severe burns.
If you notice this symptom, first turn off your car’s engine and leave the car until it cools down. Next, check the radiator cap as well to make sure your vehicle has the right amount of pressure. Too much pressure in the radiator cap will cause symptoms like this. Can I drive without a thermostat? The short-term solution to a stuck thermostat is to remove it completely.
Without a thermostat, your engine will probably never be able to reach operating temperature (unless it’s very hot outside and the car is under as much stress as it is on a race track).