Engine cooling system

The biggest cause of summer breakdown is overheating.

Hot weather and high speeds make your car work harder – but traffic jams can also take their toll. It's quite common to see cars pulled in with overheated engines in hot traffic jams. To avoid this, ensure that your coolant level is OK by making regular weekly checks – check daily if you are touring.
Checking coolant hoses and drive belts before setting out on a long journey could help you to avoid frustrating (and dangerous) roadside breakdowns. It may be a good idea to get your car serviced before embarking on a holiday.
Make sure your garage checks the coolant strength (anti-freeze) and flushes out the cooling system in line with manufacturer's recommendation.
It might seem odd to talk about anti-freeze when discussing summer motoring, however, the antifreeze solution does more than just stop the water in your engine from freezing, it also acts as a rust inhibitor – at least when it's at the correct strength (old antifreeze solution can actually corrode your cooling system).

Caution: If your engine does overheat, do not remove the radiator or coolant tank cap until it has cooled down for an hour or so – there is a danger of being scalded by super-heated steam. See Overheated Engine for more details.