In the complex world of a car’s engine, the thermostat may appear to be a minor component, but its function is crucial for maintaining the engine’s optimum performance.

For motorists travelling through Australia’s diverse climate, from the sun-baked Outback to the cooler Southern regions, understanding the role and importance of the car thermostat can be immensely beneficial.

In this detailed guide, we’ll explore the role a thermostat plays in a car, it’s functionality, common issues, symptoms of failure, and testing methods.

How the Thermostat Works in Your Car

The car’s thermostat is an ingenious component that plays a key role in regulating the engine’s temperature. Almost acting as a gatekeeper, it determines the flow of coolant through the engine and the radiator.

In a cold engine, the thermostat remains closed, allowing the engine to warm up quickly, conserving energy and reducing wear and tear. Once the engine heats up to its designed operating temperature, typically around 90-100 degrees Celsius, the thermostat opens.

This opening allows the hot coolant to pass through the radiator, where it’s cooled down before returning to the engine, maintaining a constant, optimal temperature.

The Importance of Maintaining Engine Temperature in Your Car

Maintaining the right engine temperature is critical. A car engine that runs too hot can suffer from overheating, potentially causing major damage. Conversely, an engine running too cold won’t operate efficiently, leading to increased wear, higher emissions, and reduced fuel economy. The thermostat, therefore, is key to balancing this temperature.

Symptoms of a Failing Thermostat

Recognising the signs of a thermostat in distress is crucial for timely intervention. Key symptoms include:

Engine Overheating:

The most noticeable sign. A thermostat stuck in the closed position prevents coolant from reaching the radiator, causing the engine to overheat.

Unstable Engine Temperature:

Fluctuations on the temperature gauge might indicate an erratic thermostat that randomly opens and closes.

Poor Internal Heating:

In cooler weather, a malfunctioning thermostat can prevent the engine from reaching the ideal temperature, leading to inadequate heating inside the vehicle.

Lower Fuel Efficiency:

A consistently open thermostat can prevent the engine from reaching its optimal operating temperature, leading to poor fuel combustion and reduced efficiency.

Common Car Thermostat Issues

A thermostat is a consumable part in a car engine. It can fail due to:

  • Age and Wear: Over time, the thermostat’s mechanical parts can wear out, affecting its performance.
  • Corrosion and Deposit Build-up: Accumulation of rust and debris can hinder the thermostat’s movement.
  • Gasket Failure: The thermostat gasket can fail, leading to coolant leaks and affecting engine temperature regulation.

Testing and Replacing a Car Thermostat

To test a car thermostat:

  • Remove and Inspect: Start by removing the thermostat from the engine and inspecting it for physical damage, corrosion, or debris.
  • The Boiling Water Test: Place the thermostat in a pot of water and gradually heat it. A functioning thermostat will open up at its designated temperature. Use a thermometer to accurately gauge the water temperature.

If the thermostat fails this test, it’s advisable to replace it. Replacing a thermostat is generally straightforward but crucial for engine health.

Preventive Maintenance

Regular maintenance checks are essential. During routine servicing, mechanics should inspect the coolant level, condition, and the thermostat for early signs of wear or failure. Preventive maintenance can avoid serious engine problems and extend the lifespan of your vehicle.


A properly functioning thermostat is pivotal in ensuring your car’s engine operates within its ideal temperature range. Neglecting thermostat health can lead to a multitude of engine problems. Therefore, it’s important to stay alert to the signs of thermostat failure and seek professional help when necessary.

For maintaining your car, trust the experts at Robert St Automotive. Our team of skilled mechanics specialise in comprehensive car care, including thermostat inspection and replacement. Ensure your vehicle remains in top-notch condition by booking an appointment with us. Visit our booking page to schedule your service today!