An engine thermostat regulates coolant flow in liquid-cooled engines, and can warm up the engine quickly. A typical thermostat is made up of a spring-loaded valve actuated by a wax pellet. A stuck thermostat can cause poor fuel economy, overheating, and other problems. Replacing a thermostat is usually easy.
An engine thermostat is a component that can regulate the flow of coolant through liquid-cooled engines. There are several different designs of thermostats, although they are usually contained within the cooling system and immersed in coolant. At low temperatures, they will tend to remain closed, blocking the circulation of the refrigerant through the system. This can allow the engine to warm up and run normally, at which point the thermostat can open to allow free flow of coolant. Poor fuel economy and other problems can arise if an engine thermostat is stuck open or closed.
A typical engine thermostat is made up of a spring loaded thermostatically operated valve. The valve is generally actuated by a device consisting of a wax pellet within a sealed cylinder. When wax gets hot, it can melt, expand, and force the plunger to open the valve. The wax can also contract when it cools, pulling the plunger down and closing the valve again. This can regulate the temperature of the engine within a particular range, allowing for optimal operation.
One purpose of an engine thermostat is to help the engine warm up quickly. Most liquid-cooled automotive engines use a heat sink, such as a radiator, to reduce coolant temperature. When hot coolant passes through thin radiator tubes, heat exchange can occur and lower its temperature. Without a thermostat, engine coolant could circulate through the radiator as soon as a vehicle is started, preventing it from getting hot. This could prevent the engine from reaching operating temperature or simply extend the warm-up period.
If an engine thermostat is open, a similar problem can occur. The coolant will tend to take a long time to warm up and engine performance may be affected. This could show up in reduced fuel consumption or other issues. Since hot engine coolant can also pass through the heater core to heat the passenger compartment, a stuck thermostat can also cause poor performance of this system.
More serious consequences can arise from an engine thermostat that is stuck closed. If the thermostat never opens, it can prevent coolant from circulating through the radiator. This can cause the engine to overheat, resulting in irreparable damage to a variety of systems and components. The head gasket could fail or other components could be damaged and require costly repairs.
Replacing an engine thermostat is often an easy operation, although some vehicles can present a challenge. Many thermostat housings are located on the engine block and attached to the upper radiator hose, making it easy to locate and replace. Other vehicles have thermostats that are in more difficult places, such as on the bottom of the engine. In either case, replacing an engine thermostat is usually a matter of removing the housing, installing a new unit, and then bleeding the air from the cooling system.
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