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Summer heatwave: is your car ready?

Steam coming from car engine

The average British summer isn't renowned for being particularly hot, but global warming means that heatwaves are becoming more common.

Summer heat presents a whole different set of challenges to winter. No longer do you have to worry about having enough traction to make it up that hill, but you do have to worry that your car's cooling system can handle a mile-long climb in sweltering heat. You may not have to worry about the cold lowering the cranking output of your battery, but you do have to worry about a hot engine compartment literally boiling the battery, for a similar effect.

Here's what you need to check on your car before the mercury soars.

1 Oil check and change

When was the last time you did an engine oil check? And how about a change of oil? These days, most modern cars have a computer that tells you when to get your oil changed, but if yours doesn't, you should be sure to change it on time.

In the old days, cars would use a thinner oil in winter and a thicker viscosity in summer, but modern multi-weight oils have mostly done away with that.

But if you take a lot of short trips in the dead of winter, your oil may not be able to evaporate out all the condensation, which can lead to internal rust and corrosion.

That is why a fresh change of oil after a long cold winter is still required, even if you use the same weight oil year-round.

2 Coolant/antifreeze 

Antifreeze is vital year-round, protecting from sub-zero temperatures in the winter and keeping the engine cool in the summer, as well as providing protection against corrosion - something that plain old water won't do.

Start by making sure the system has enough fluid; with the engine cold fill the radiator to the top via the cap (if it has one), then fill the coolant expansion tank to the 'max' line. Make sure you're using the right type of coolant for your car (your handbook and Haynes manual will specify).

Most modern cars have a recommended coolant change interval of 100,000 miles or five years.

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Bulge in car tyre

3 Check your tyres!

Many modern cars go without a spare tyre, sending their driver out into the world with a can of sealant, which is why regularly checking the condition of your tyres is so important. If you don't have dedicated winter and summer tyres, now is the time to check your all-seasons for wear and damage.

The potholes and frost heaves of winter roads can cause sidewall damage, such as the bulge seen above, which can cause a dangerous blowout if left to get worse.

Scorching Tarmac causes accelerated wear on your tyres, too, so be sure they have plenty of life left in them. Often you can get a free or discounted alignment with purchase of new tyres, and after a rough winter, your car would probably benefit from that too.

4 Belts and hoses

The other major rubber parts of your vehicle, and the other major wear items in your cooling system, are the belts and hoses. The hoses, of course, carry coolant from the radiator to the engine and connect the heater core to the rest of the cooling system.

When the ambient temperature goes up, stress on the cooling system goes up, and the hoses have a tougher time containing the pressure/ Look for signs of bulges or collapse, and check for cracks that may start out cosmetic but can become leaks.

The belt (or belts) also have a harder time in the summer because of the air conditioning compressor, which on average needs the equivalent of 10bhp to run, not to mention the electrical requirements of the clutch in the system and the blower motor. Look for signs of cracking or shiny spots where the belt has been slipping.

5 Air conditioning

Now is the time to test your air conditioning and make sure it still blows ice cold. If you can't make cold air come out of the vents, and the AC compressor clutch is engaging, the most common issue is a leak causing low refrigerant.

Your local car parts store sells leak detector kits, allowing you to look for telltale red dye drips or a spray of gas which glows in UV light. There are also recharge/sealant kits which can replace the R-134a and seal up any tiny holes where it is leaking out.

It's important to use your air-con throughout the year - yes, even in winter, when you can turn up the heater controls and use the AC to keep windows fog-free more effectively.

Frequent AC operation ensures the system's rubber seals are kept lubricated, minimising the risk of the gas leaking out over time.

6 Battery

One of the last things to check is the battery. These days, most people don't check the water level of their battery or test it with a hydrometer, and that's fine because most batteries are made to work with little maintenance for 3-5 years. And anyway, some batteries are maintenance-free, so you can't access the liquid within.

However, since it can take a significant amount of juice to crank a hot engine in the summer, you do need to make sure everything is up to spec. Here are the details on How to Test a Battery with a Multimeter.

Now is also a good time to go over the terminal ends and other connections and make sure they are clean and tight as well; since chemical reactions happen faster at higher temperatures, that corrosion will get much worse if left over the summer.