Everyone remembers winter prep, but summer prep matters just as much. Heat destroys your car differently from frost. The engine overheats, the battery dies silently, tyres lose stability on scorching tarmac, and a broken A/C turns every drive into misery. Here is what to check before temperatures cross thirty degrees.
A/C: check it before the first heatwave
The worst thing is discovering that your A/C does not cool on the first 35-degree day. Turn it on while outside temperatures are still moderate and check whether it blows cold. If the air from the vents is not cold after five minutes or you notice an unpleasant smell when it kicks in, the system needs servicing.
The most common reason for weak cooling is low refrigerant. The A/C system is not hermetically sealed because operating pressure constantly stresses fittings and hoses, so small amounts of gas escape over time. A refrigerant top-up takes half an hour and fixes the problem in most cases. But if refrigerant disappears noticeably faster than normal, there is a leak somewhere that needs to be found and repaired, because topping up without a fix means the same loss again in a few months.
The cabin filter (pollen filter) directly affects airflow through the A/C. A dirty filter reduces airflow, forces the compressor to work harder, and lets less cooled air into the cabin. Replacing it once a year, ideally before summer, keeps the A/C efficient and the cabin air cleaner. If the A/C has not been serviced in a while, disinfecting the evaporator removes bacteria and mould that develop behind the dashboard and cause that stale smell when you first turn the system on. Details on what an A/C service covers are in our guide to A/C servicing and refrigerant recharge, and if it is time for a service, check our A/C service page.
Cooling system under summer load
In summer the cooling system operates at its upper capacity limit. Ambient air temperature is high, the A/C puts extra load on the engine, and in a traffic jam at the city entrance or a border crossing the engine gets almost no airflow through the radiator. Under those conditions, any weakness in the cooling system becomes critical.
Start with the coolant level. The expansion tank has min and max marks, and the level on a cold engine should sit between them. Coolant is not just anti-freeze. It raises the boiling point, protects metal surfaces from corrosion, and maintains efficient heat transfer. If the fluid is older than 3-5 years or has changed colour (turned cloudy, brown, or shows visible sediment), replacement is due. Details on coolant types, colours and mixing rules are in our guide to coolant and antifreeze.
Inspect the rubber cooling hoses. A hose that feels soft to the touch, is cracked or bulging at the joints is a candidate for bursting in the heat, right when system pressure is highest. The radiator fan is equally important: if it does not kick in when temperature starts climbing toward the red, the engine will overheat in the first traffic jam. A thermostat stuck in the closed position has the same effect because it blocks coolant flow to the radiator. More on the thermostat, radiator and overheating signals is explained in our cooling system guide.
Tyres on hot tarmac
Temperature directly affects tyre pressure. For every 10-degree change in ambient temperature, pressure shifts by roughly 0.1 bar. Tyres that were at the correct pressure in winter may be over-inflated in summer, while tyres that were slightly low in spring may end up just right on hot asphalt. The problem is that most drivers never check pressure between seasons.
Measure pressure in the morning while tyres are cold (before driving or after the car has sat for at least two hours). The recommended pressure for your vehicle is on the sticker inside the driver's door frame or in the owner's manual. Do not use the number printed on the tyre sidewall, as that is the maximum pressure the tyre can handle, not the optimum for your car.
Inspect tyre condition too. Cracked sidewalls, shallow tread or uneven wear mean the tyre is not safe for a long drive in the heat. Tyres older than 5-6 years lose elasticity even with adequate tread and are more prone to sudden blowouts at high temperatures. Read the manufacturing date from the four-digit DOT code on the sidewall (e.g. 2221 means week 22 of 2021).
Battery: heat kills it silently
Most drivers think the battery is a winter problem. It is true that a flat battery usually shows up in winter, when the engine needs more cranking power. But it is summer heat that actually kills it. High temperatures speed up chemical reactions inside the battery, increase electrolyte evaporation and accelerate plate degradation. Winter then simply finishes off what summer damaged.
A battery that is 4-6 years old should be tested before summer. A load test takes a minute and shows how much power the battery can actually deliver, not just open-circuit voltage. If capacity is below 70-75% of nominal, replacing it before summer is a smart move, because swapping a battery at the shop is much easier than waiting for roadside assistance in 40-degree heat.
Wipers and washer fluid
On a summer drive, especially at night, insects on the windscreen are a serious visibility hazard. A single layer of squashed bugs at 100 km/h combined with a low sun or oncoming headlights can completely block your view for several seconds.
Fill the washer reservoir with fluid that contains an insect-removal additive. Plain water does not dissolve stuck-on insects effectively and quickly leaves smears. Check that the wipers clean the entire windscreen surface properly. Rubber blades that spent the winter under snow and ice often harden, crack and start smearing instead of cleaning. Replacing wipers is one of the cheapest items on a car, yet it directly affects safety.
Overheating in traffic: what to watch and what to do
The riskiest scenario for overheating is standing in traffic in the heat with the A/C running. The engine is working, producing heat, the A/C adds extra load, and airflow through the radiator is minimal because the car is not moving. The radiator fan then takes over all the cooling.
Watch the temperature gauge. Under normal conditions it sits steadily around the middle of the scale. If it starts creeping toward the hot zone, act immediately: turn off the A/C (reducing engine load), turn the cabin heater to maximum (the heater core acts as an extra radiator by drawing heat from the coolant), and open the windows. If the needle keeps rising, switch on your hazard lights, pull over at the first safe spot and shut the engine off. Do not open the expansion tank cap while the engine is hot, as the fluid is under pressure and can cause burns.
If you are planning a longer summer trip, especially to the coast, also check our guide to preparing for a longer journey, which covers brakes, documents, the spare tyre and other items important for travel. And if you want us to check all of this in one go, book an appointment and we will get your car ready for summer.