Keep Your Eye on the Thermostat

The sudden failure of an inexpensive part can leave you and your vehicle stranded by the side of the road. This is especially true of the cooling system thermostat. The thermostat resides in between your engine and your radiator and acts as a temperature controlled engine coolant valve. If the valve fails, so does your cooling system and an overheated engine, and driver, often are the unfortunate end result. The good news is thermostats are inexpensive and relatively easy to replace.


The primary function of the thermostat is to allow the engine to warm up quickly by controlling coolant flow to the radiator. When you start your engine the controlled explosion known as internal combustion begins. As heat builds inside the cylinders, the coolant in the passages around them begin to absorb that heat. The thermostat opens to allow coolant flow only after the engine reaches proper operating temperature. Hot coolant flows away from the engine and into the radiator to cool off. Seconds later it returns to the engine to absorb more heat. So goes the operation of your vehicle cooling system.

Getting Started
Getting your engine to operating temperature quickly helps with fuel consumption as well. Sensors peering into engine coolant tell the computer how much fuel to add, and at what idle speed to run the engine on cold start. This is why your engine runs a little faster when you first start it up. Fuel is added in greater quantities and RPM is increased to prevent cold stalling. In colder climates getting the engine warm fast also means you get warm too, as your heater operates by way of toasty warm engine coolant.


The thermostat has a secondary function of regulating coolant to maintain optimal engine operating temperature and cooling system efficiency. Each thermostat has a temperature rating at which it will open fully. Engines are designed to run most efficiently at a certain temperature, and for this reason, it's important to always replace your thermostat with another of the correct temperature rating. Installing a 160-degree thermostat into an engine designed to operate at 195 degrees may cause poor fuel economy, as the computer will meter an incorrect amount of fuel.