Automotive Thermostats


An automotive thermostat is a simple but absolutely vital component of a vehicle’s cooling system. It makes it possible to regulate the temperature of the engine.

How does a car thermostat work?

In a vehicle, the thermostat measures the temperature of engine coolant and includes a valve with a spring.

When the engine coolant is below a threshold temperature, the thermostat valve stays closed. This keeps the coolant in the engine system.

Once the vehicle’s engine reaches its full operating temperature, the valve opens up, allowing coolant to flow into the radiator. There it will be cooled before the water pump moves it back to the engine.

During vehicle operation, the thermostat isn’t completely open or closed. It continually adapts, opening wider or partially closing to control the flow of coolant. This regulates the engine’s temperature.

Symptoms of a faulty car thermostat

The most obvious consequence of a broken car thermostat will be engine under heating or overheating.

In a worst-case scenario, overheating can lead to irreversible engine damage.

Other possible signs of a broken or defective thermostat can include:

  • erratic temperature fluctuations on the engine temperature gauge
  • coolant leaks under the vehicle (look for orange or green puddles)
  • leaked coolant around the thermostat housing.

Checking if a car thermostat is working

You can check for proper functioning of the thermostat. To do this, first let a car idle for a few minutes, remove the radiator cap and check for flowing coolant.

At this point, the engine will still be cold – so no coolant should be flowing.

Then once the car has been driven and the engine is hot, check again that coolant is flowing. If it isn’t, something is wrong with the vehicle’s cooling system. The problem could be a malfunctioning thermostat with a valve stuck in the closed position.

How to replace a car thermostat

It’s reasonably easy and inexpensive to replace an automotive thermostat. However, if you aren’t a mechanic yourself, it’s best to have a problem with a car’s cooling system diagnosed by an expert (in case it’s not the thermostat that’s at fault).

For step-by-step instructions, see our article How to Replace the Thermostat on Your Car.

To help visualise the process, you may also want to try this YouTube video.

High-quality automotive thermostats for sale in South Africa

Masterparts offers thermostats that:

  • are comprehensively tested
  • meet or exceed original equipment (O.E.) specifications
  • are suitably calibrated for South African climactic conditions.

Thermostat brands we offer include Thermocool, Original Birth and MotoRad.

Where to get thermostats from Masterparts

We offer door-to-door delivery of thermostats and other automotive parts and spares. Alternatively, visit any of our branches across South Africa or in Windhoek, Namibia.

Thermostats in and around Cape Town:

Thermostats in KwaZulu-Natal:

Thermostats in Namibia:

Masterparts stocks more than 50,000 car parts and spares (including high-quality automotive thermostats), for more than 3,500 vehicle models. Contact us if there’s a part you need and we’ll do our best to help.


Call us on 021 657 5757 or complete the form below to get a quote.

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