How to keep your cool in the hot season

For the next few weeks, your car’s cooling system will have to work harder than at any other time of the year. 

In this hot season, blazing sunshine will bounce off the tarmac at more than 60 degrees. Healthy vehicles will easily cope with  the higher air temperatures, but any minor weakness in the cooling system could turn into a major breakdown. 

And the list of possible insipient weaknesses is not short. Here’s why: On any trip, your engine is generating heat – like a fireplace! – through combustion of fuel and added friction. If it was not cooled, the metal would expand and the moving parts would jam solid (“seize”), scratching, burning, bending and snapping all sorts of components in the process. 

The first and last line of defence is engine oil, which reduces friction and absorbs and dissipates some of the combustion heat. If the oil level is too low, or its condition is weak or dirty, more frictional heat can overwhelm even a good cooling system (and burn the oil itself). 

SMOOTH FLOW

Next, further and essential cooling is provided by a robust flow of water – with or without additives, and technically known as “coolant” –  pumped through a “jacket” of channels around the inside of the engine casings (where it collects heat) and then circulates on through hoses to the radiator (where it is cooled by the passage of air) on its way back to the engine again.   

There must be enough coolant (check) and there should be no leaks… anywhere (check). It must be pumped round at the right speed; not so fast that it doesn’t have time to cool in the radiator; not so slowly that it spends too long in the engine and vaporises. The flow is generated by the water pump (check) which is driven by a fan belt (check) which is carried on pulleys (check) which have lubricated bearings (check); and flow is controlled by a self-adjusting valve called the thermostat fitted in the coolant cycle between the engine and radiator.    

The coolant must flow well through all the channels, which can get bunged up with rust and dirt (check). Using only very clean and pure water and designer additives can help prevent that.   

The coolant must be kept under the right amount of pressure – enough to stop water  turning to steam in places where it reaches temperatures well above 100 degrees C, but not so much that it bursts hoses and radiator seams. The radiator cap has a pressure spring that organises that balance… if it has the right rating and is working properly (check).   

And there must be plenty of air passing through the radiator fins and over the engine to carry the captured heat away. The car’s own motion is usually enough when cruising, but at low speeds or in traffic or under extreme load, extra air flow must be provided by a fan – driven by a belt on more pulleys (check, check) or a temperature-triggered electric motor (check). 

And the radiator itself should not be blocked by dirt – inside or out -  or by fin damage (check, check) or ill-placed accessories.  So checking your cooling system is not one or two items. It’s more than a dozen. 

And add another: develop a habit of regularly checking your temperature gauge when driving.