A little known, relatively inexpensive device called an engine “Thermostat” can make a big difference Engine Power, Fuel Economy and Emissions!

Firstly, what does a thermostat do?

Car thermostat

Just like the “thermostat” in your hot water cylinder at home controls the temperature of hot water, your car engines “thermostat” controls the temperature of your engine.

The purpose of an engine thermostat is to regulate the engine temperature via controlling the flow of coolant through the engine and radiator. The thermostat does this by opening and closing, thereby managing the flow of coolant into and around the engine as it is needed.

When your car’s engine is still cold, the thermostat will remain shut. This allows the coolant to flow solely around the engine components (and not the cooling system radiator) allowing the engine to get up to the desired operating temperature of around 85 degrees Celsius as quickly as possible.


The thermostat has a preset temperature at which it is designed to operate to keep your engine at peak operating and fuel efficiency. A correctly working engine thermostat and cooling system will maintain your engine at a fairly constant temperature.

If your car has a temperature gauge you should see that it rises fairly quickly to halfway (say within 3 to 5 km of driving from cold starting), and then the temperature gauge should stays constantly at about half way.

Once the engine’s temperature reaches a certain level, the thermostat will begin to open, releasing coolant into the radiator ensuring your engine does not overheat.


What are the symptoms of a faulty thermostat?

  • Engine overheating
  • Engine running too cold (temperature gauge takes more than 3 to 5 km to get to half way)
  • Major fluctuations in engine temperatures while driving.
  • Coolant leaking around the thermostat area.
  • Excess fuel consumption
  • Excess exhaust emissions


What if the thermostat becomes stuck closed?

car temperature gauge

If your vehicle’s thermostat is unable to open, coolant won’t be able to flow into your radiator for cooling. Since the radiator and coolant regulate your engine’s temperature, your car will have no way to cool itself down. This will result in overheating of your engine.

If your engine’s temperature gauge is reaching a high level after 5-15 minutes of use, this may be because your thermostat is not opening when it needs to. Overheating engines are one of the most expensive parts of a car to fix. Therefore if you suspect your engine to be over heating, we recommend that you get it tested immediately, to avoid costly damage.

What if the thermostat becomes stuck open?

If your car’s thermostat is stuck open, your engine will not be able to reach its optimum temperature.

When an engine starts, the thermostat remains closed until the cooling system fluid that is circulating in the engine block, cylinder head and intake manifold reaches a preset temperature. This allows the engine to reach the optimum operating temperature as quickly as possible.

If this engine operating temperature level is not reached, your vehicle will have increased fuel consumption and exhaust emissions plus possibly less power.

You may also notice that the engine RPM remains higher than normal for longer, and the cars temperature gauge on the dash may stay below half way for a long period (more than 3 to 5 km).


What happens when a thermostat is inaccurate?

Sometimes, a faulty thermostat will not respond as expected. This will result in the thermostat opening and closing at the wrong times. If your engine temperature is fluctuating, this may be a sign of an inaccurate thermostat that needs replacement.

At Grimmer Motors, we are able to examine, repair and replace your vehicle’s thermostat. We are also able to diagnose and fix several other cooling system related problems. For reliable cooling system, radiator and thermostat servicing in Hamilton, contact us today!

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