What Can a Bad Thermostat Do?
The thermostat regulates the flow of coolant within the engine of a car. Thermostats are not interchangeable among vehicles, as each engine ...
The thermostat regulates the flow of coolant within the engine of a car. Thermostats are not interchangeable among vehicles, as each engine has a specific thermostat design set to open at a certain temperature. A thermostat, shaped like a top, has an interior spring or coil and plate atop the coil. As the engine warms, the coil expands and moves the plate, which acts as a gate to allow coolant flow through the engine. When the thermostat malfunctions, the coil doesn't open at the right temperature.
Cooling System
The cooling system consists of the radiator that holds the coolant, an overflow container, a water pump, belts, cooling fan, hoses running to and from the engine at specific locations, clamps, various sensors and a thermostat. The thermostat allows the coolant into the engine at the set temperature for the engine. The engine contains water channels the coolant runs through to absorb the heat from the engine to allow it to operate efficiently. As the coolant flows through the engine it picks up the heat caused by engine friction and combustion and takes the heated coolant back to the radiator for air cooling and recycling. A functioning thermostat is critical to system operation.
Closed Thermostat
In the worst-case scenario, when the thermostat won't open, the engine doesn't cool and rapidly overheats. The engine block type makes a difference in the damage a bad thermostat causes. As an engine overheats, pressure builds and can blow out head gaskets -- a costly repair. In engines with aluminum blocks (most cars today), the damage can be severe; the head can warp under extreme heat, necessitating replacement.
Open Thermostat
A thermostat that stays open usually isn't a big issue in the summer and is more noticeable in the winter. The vehicle's heater runs from the warmth of the cooling system. If you note the heater isn't getting hot, one cause may be the thermostat is staying open. This is not as serious as a closed thermostat, but it is still important to replace a thermostat that stays open. Engine thermostats are set to open at generally between 190 to 200 degrees F. An always-open thermostat doesn't allow the engine to reach normal operating temperature, which prevents complete burning of fuel and causes fuel to condense inside the cylinders. This affects a vehicle's gas mileage and your wallet.
Overheating
If you recently fixed an overheating problem, say a broken or leaking radiator or water pump, but didn't change the thermostat, you still may experience engine overheating because the thermostat won't open. Excessive engine and coolant heat can cause the thermostat to fail permanently. When making a repair to any part of the cooling system because of overheating, it's a good idea to change the thermostat as well. It's a relatively easy process, does not cost much, and it can save you thousands on future engine repairs.
