Radiator Coolant and Thermostats
coolant flow and thermostat diagram

Mick Farmer specialises in 4WD driver training for organisations like the United Nations, who service developing African countries, particularly in Uganda. Off-road driving conditions on the African and Australian continents are similar in many respects and much of what Mick says is relevant to us over here. The obvious major difference is that here, we don't have to negotiate too many land mines, and it's not an everyday occurrence that someone shoots at you as belt across the Nullarbor.

Here Mick talks about radiator coolant and thermostats. A thermostat is a temperature sensitive device installed in the cooling system that restricts fluid flow as engine temperature drops, maintaining constant and correct engine temperatures. Removing the thermostat used to be common practise in Australia but it's done less and less these days. Nonetheless, it's still a valid point. As Mick points out, coolant is extremely important to modern engines. On a side-note, generally speaking different coolants should not be mixed. Toyota vehicles (2WD or 4WD) normally require Toyota's proprietary radiator coolant. There's a mountain of anecdotal evidence around supporting the exclusive use of Toyota coolant in Toyotas and others whose experiences suggest it isn't an issue.

The article -

In Uganda, like the rest of East Africa, mechanics always remove the engine thermostats when the car first arrives in the country. They call this tropicalising the vehicle. And as for coolant, the owner is told, that is only necessary in cold countries - water is good enough.

Every week I see vehicles with either one or both missing. The owner/driver of the vehicle looks at me blankly when I say that they are necessary to maintain the correct running temperature of a vehicle. "But it has been running like this now for ages", they say. "It won't be for much longer", I reply, "and you'll soon have a hefty repair bill to boot". This usually grabs their attention!


Coolant or antifreeze, as it is known in colder climates, is recommended by all vehicle manufacturers. Anyone who has run a vehicle in a cold country knows the importance of antifreeze but why then should we put it in our vehicle in a hot country? The answer is two fold.

Firstly, coolant has a corrosion inhibitor, which does what it says. It prevents the build up of corrosion in the cooling system. I'm sure everyone is aware that if you leave a sheet of steel open to the elements it quickly gets covered with rust. This is exactly what happens to the cooling system of your vehicle if run with water only. Eventually the corrosion will build up until it starts to effect the efficiency of the main parts - i.e. the radiator, the water pump, the thermostat and the hoses.

Secondly, coolant raises the boiling point of the cooling system. Therefore, if part of the system does fail and the engine does start to overheat, less damage will occur as fluid loss by vapour evaporation is kept to a minimum.


On then to thermostats. Too often I hear people and so called mechanics saying that thermostats aren't necessary in a hot climate. A thermostat controls the internal temperature of the engine and keeps that temperature constant. Most engines are designed to run at a temperature of 80 degrees Celsius and above.

I would like any one to name me a country that has a temperature that high! If you run without a thermostat then parts of the engine will run too cool and this can cause accelerated wear. Also, the engine as a whole, will be running at uneven temperatures and therefore, is susceptible to failures. Especially if the engine is made from dissimilar metals i.e. steel engine block with an aluminium cylinder head. If your thermostat becomes faulty by all means take it out, but make sure another correct one is put in its place.

So, if you're unsure get it checked and put right. In the long run it will be cheaper and more reliable!! Safe and happy motoring.

Another important maintenance item. We take a look at - Air Filters

This article is published under CCL

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