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Checking your coolant and cooling fan

Engine temperature maintenance

Most modern cars have a sealed cooling system so they shouldn’t need any topping up – unless, of course, they’ve sprung a leak.

Give your engine coolant and your cooling fan a check every couple of weeks so you can spot any problems early. It’ll only take a few seconds and could save you a lot of money and hassle.

How to check your coolant

1. Find the expansion tank

  • It's essential to correctly identify the expansion tank.
  • Check the vehicle handbook for the location of the coolant filler cap.
  • Follow any vehicle-specific advice given (adding antifreeze to the screen wash, brake fluid or power steering reservoir would be a very bad idea.)

2. Check the coolant level

  • The coolant should be between the min/max marks on the side of the expansion tank.

3. Check hoses for problems

  • Check any hoses that you can see at the same time.
  • Wet or white staining is a sign of possible problems to come.

4. Top up if necessary

  • If the coolant needs topping up, don't remove the filler cap unless the engine is cold – you could be scalded by a sudden release of pressurised hot water.
  • Make sure you use the right sort of antifreeze – the different types don't mix well.
  • Antifreeze doesn't just protect your engine in winter. It helps stop corrosion and scale build-up all year round.

5. Take it to a garage

  • It's not normal for the coolant level to drop.
  • If you see that it has, get a garage to take a look.

Engine coolant

How to check your cooling fan

When your car's moving, air flows through the radiator to keep your engine's temperature 'normal', but if you stop – in a summer traffic jam for example – your engine has to rely on a thermostatically controlled electric cooling fan to force air through the radiator.

It’s important to check regularly that the fan and temperature sensor are working. Here's how:

  1. Set the car heater to cold.
  2. Run the car until the engine reaches normal temperature.
  3. Allow the engine to idle for around five minutes.
  4. Watch your temperature gauge – don't allow the car to overheat.

Cooling fans should cut in automatically. If they don’t there may be a fault with the fan temperature sensor, the wiring or the fan itself.

Ask your local garage to give it the once over.

Here's a step by step guide showing how to check your cooling fan.

Woman looking at overheated engine with steam coming out

How do cars overheat?

If you never check your car's coolant level, you could face a hefty repair bill if your engine overheats.

At best it could be a couple of hundred quid to repair the cooling fan, more than that to replace the head gasket, or at worst, it could be over a thousand pounds for a new engine.

Why do engines overheat in summer?

Overheating is a much bigger problem during the summer than in the winter as engines operate at higher temperatures. There isn't the cold winter air to take away a lot of the heat.

Many cars are only used on the same local trips with the engine barely reaching normal operating temperature, so the cooling system is hardly tested.

However, that all changes when the car is suddenly loaded with luggage and passengers for a long holiday trip in hot weather, exposing any problems in the system.

How to avoid your engine overheating

There are a few steps you can take to avoid your engine overheating.

Drivers should get into the habit of regularly checking their car including the coolant level and fan. If you notice that the coolant has dropped, get it checked out, as modern cooling systems shouldn't really need topping-up between services.

Here's what you can do to keep your engine cool:

  • Check your coolant level using our simple steps.
  • Check your cooling fan - a seized cooling fan is the most common cause of initial overheating.
  • If the temperature gauge rises, the most effective way of temporarily dealing with it is to turn the heater up full and the air conditioning on.

Published: 14 April 2016 | Updated: 18 September 2019

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