5 surprising things your car does in summer

The summer months are hard on cars – they have to battle against baking sun, busy traffic and humid conditions, hopefully without missing a beat on the high-mileage trips they're pressed into.

Cars largely cope fine, thanks to decades of design evolution. However, they do still have some surprising tricks that only come out in the summer months – and if you're not fully aware of them, these can be alarming.

Here, we outline five eye-opening things you may find your car doing in the summer... and also explain why they happen, to put your mind at rest.

Drips from beneath

Many people are alarmed to see pools of water form beneath their car when they park up. It can also sometimes be possible to see water dripping from cars on the move, too.

This is caused by the air conditioning system. It is condensed water dripping from the evaporator and it is designed to be released in this way. Air conditioning does not only cool water, but dehumidifies it... and that water has to go somewhere!

Smoke from the air vents

Plumes of white smoke coming from the air vents when you turn on the car is extremely alarming. However, it is nothing to worry about (unless the smoke is acrid). It is caused by the car's air conditioning unit battling agains the hot weather.

The smoke is water vapour from the hot humid air. Passing it too quickly through the air conditioning system will not give the condensing moisture time to form into water droplets. It instead carries on straight through the system to cause the 'smoke'. Running the system for a while will stop it.

Roaring from the engine bay

In slow traffic, it can be alarming to hear a rushing, roaring noise coming from the engine bay. This often comes and goes, but stops again when you are on the move.

The noise is the engine cooling fan cutting in and out. To save fuel, this does not run all the time, but kicks in when the engine water temperature rises too high. Once you are moving again, the flow of air through the radiator grille will ensure it is not needed.

Becomes sticky

If you park under a tree in the summer, you may not notice the effects until you run your hand over the paintwork – then you'll discover sap from the tree has collected in tiny sticky droplets all over your car.

If it is left, the sap will harden and can cause paint damage: it is best removed with lots of water and a hot, soapy shampoo solution. It also covers windscreens too: this is why you need a good summer solution fluid in the windscreen washer bottle (and plenty of it).

Becomes slower

Sensitive drivers may notice their car feels more lethargic in the summer months, particularly if the engine is smaller and less powerful. Acceleration can seem slower and response not quite as crisp as in the winter.

This is because hot summer air is less dense (the mass of air divided by its volume), and so creates a smaller 'bang for your buck'. The difference isn't great but it does knock a little off engine performance, and can also affect fuel economy too. The flipside is, engines will perform better on cool, crisp mornings!