Driving in Hot Weather: How to Protect Your Car This Summer

Why summer driving is harder on your car than you think

Most drivers associate winter with car problems — dead batteries, frozen locks, icy roads. Summer brings a different set of stresses that are easy to overlook until they cause a breakdown. High ambient temperatures raise fluid temperatures, increase tyre pressures, and work the cooling system harder than any other season.

Coolant and the cooling system

Your engine's cooling system works hardest when ambient temperatures are high. If the coolant level is low, or the antifreeze concentration is incorrect, the system has less capacity to shed heat — and overheating risk rises. Check the coolant level in the expansion tank when the engine is cold. The level should be between the MIN and MAX marks.

If your coolant looks rusty or has visible debris in it, it is due for a change. Degraded coolant loses its corrosion inhibitors and can begin to attack the aluminium components in the cooling system. A coolant flush and refill every three to five years is inexpensive prevention against a radiator or heater matrix leak.

Tyre pressure rises in heat

Tyre pressure increases as temperature rises — roughly 1 PSI for every 10°C of ambient temperature increase. A tyre correctly inflated on a cold morning can be significantly over-pressured by afternoon on a hot day. Over-inflated tyres have a smaller contact patch, which reduces grip and makes the ride harsher. They also wear faster in the centre of the tread.

Check tyre pressures in the morning before driving when the tyres are cold. The correct pressures are in the handbook or on the sticker inside the driver's door. Do not let air out of a warm tyre to match the cold specification — wait until the tyre has cooled.

Battery and electrics in summer heat

Car batteries are commonly associated with winter failure, but heat is equally hard on them — high temperatures accelerate the chemical degradation inside the battery. A battery that just got through winter may fail during a summer heatwave, particularly in a car that sits in direct sunlight for hours.

If your battery is more than three years old and you notice sluggish starting or the stop-start system deactivating itself, have it load-tested before summer road trips. A load test takes a few minutes and tells you definitively whether the battery has enough reserve capacity for reliable use.

Air conditioning and cabin comfort

Air conditioning systems lose approximately 10% of their refrigerant each year through normal permeation. A system that cooled adequately last summer may be noticeably weaker this year. An air con regas restores the refrigerant charge and is a quick job — usually under an hour. If the system produces cool air initially but then blows warm, or if it never gets properly cold, a regas is the first step.

If a regas does not restore cooling, the system may have a leak or a faulty component that needs diagnosis. We handle both at The Car Guys. Book an air con regas online or call 01527 336608.