Engine Cooling System Thermostat
When a thermostat malfunctions it can stick closed not allowing the coolant to circulate causing the engine to overheat. Or the thermostat could stick open causing the engine to run too cold. In this case the service or check engine soon light could illuminate, followed by a trouble code. Test Procedure: To test a thermostat remove unit. Prepare a pan of water deep enough to cover the thermostat completely. Next install a temperature gauge into the water along with the thermostat. A cooking thermometer works well for this. Next, start heating the water while watching gauge, the thermostat should remain closed until the water reaches 190° at this point the thermostat should start opening and be completely open at about 195°. If the thermostat stays closed through the boiling point the thermostat has failed and needs replacing. If the thermostat is stuck open or broken it has failed and needs replacing. Never run an engine without a thermostat because the thermostat works as a system flow regulator as well. What this means is the thermostat has a specific opening that regulates the flow through the cooling system. If the coolant is allowed to flow to quickly through the radiator the coolant will not have time to transfer the heat it has absorbed. This will cause the engine to overheat.
Red and Green Engine Coolant In the beginning, water was used for cooling systems as it is the most efficient fluid to absorb and dissipate heat. The disadvantage of using water is that it freezes and will rust. Then water was mixed with ethylene glycol which worked as an antifreeze element. Not only does the freezing point improve so does the boiling point by adding ethylene glycol. Ethylene glycol can be heated up to 250°F before becoming ineffective. The cooling system is pressurized to 18 psi. to increase coolant boiling point which adds 9 degrees Fahrenheit to the boiling point of the coolant. Coolant is also used to avoid corrosion. An engine thermostat is designed to stop the flow of coolant from the engine to the radiator. This temperature sensitive valve is designed to open when the engine has reached operating temperature (190°-198° F). This operating temperature is used to help facilitate the fuel combustion process.
- Low levels of coolant can lead to problems related to engine overheating. Always maintain proper levels of coolant in the overflow coolant reservoir tank. ONLY! Check the radiator when the engine is cold. Only add antifreeze and reinstall the cap properly. Always drain and refill your cooling system regularly.