News

Summer Heat Checklist: Cooling, AC and What Fails in Hot Weather

Heat is harder on a vehicle than cold in several respects. Cooling margins shrink, rubber and plastic age faster, and the systems working hardest — cooling and air conditioning — are the ones most likely to leave you stopped at the roadside. A check before summer is worth more than a repair during it. Cooling System This is where summer failures concentrate, and where the consequences are most expensive. Coolant level and condition. Old coolant loses its corrosion inhibitors. If it looks rusty, murky or has debris floating in it, it is overdue. Hoses. Squeeze them when cool. They should feel firm but pliable — not rock hard, not spongy, and with no swelling near the clamps. The radiator core. Clean out bugs, leaves and road debris from the fins. A blocked core is a common cause of summer overheating and is easy to overlook. The radiator cap. It maintains system pressure, which raises the coolant's boiling point. A weak cap causes boiling at normal temperatures. The water pump. Check for coolant residue around the weep hole and for play in the pulley. The cooling fan. On electric systems, confirm the fan runs when the engine is hot or the AC is on. On belt-driven systems, check the fan clutch engages when hot. A useful diagnostic distinction: overheating only at idle or in slow traffic points at the fan or fan clutch. Overheating at all speeds points more toward the thermostat, water pump, radiator or coolant condition. Air Conditioning Run it before you need it. Discovering the AC is dead on the first 35°C day is a common and avoidable annoyance. Check that the compressor clutch engages — the centre plate on the compressor pulley should spin when the AC is on. Clean the condenser at the front of the vehicle. It sits ahead of the radiator and collects the same debris. Replace the cabin air filter. A clogged filter reduces airflow badly and is cheap to change. Note whether cooling is weak only at idle — that usually indicates airflow rather than refrigerant. If the system is low on refrigerant, it leaked. Refrigerant is not consumed in normal use, so a system that needs topping up every summer has a leak that will eventually take the compressor with it. Tires Heat and tires deserve serious attention. Under-inflated tires build heat as they flex, and heat is what causes blowouts. Check pressures when cold, and check more often in summer. Pressure rises as ambient temperature climbs, but starting under-inflated is still the dangerous condition. Inspect sidewalls for cracking, bulges or cuts. Heat and UV accelerate rubber ageing. Check the age of the tires. Rubber degrades over time regardless of tread depth, and old tires are more prone to failure in heat. Check tread depth, and do not forget the spare. If you tow or carry heavy loads in summer, verify the load rating and adjust pressures accordingly. Battery Cold weather gets the blame for battery failure, but heat does more of the actual damage. High temperatures accelerate internal degradation and evaporate electrolyte. A battery weakened over summer is often what fails on the first cold morning. Check terminals for corrosion and tightness. Check the resting voltage. Confirm the hold-down bracket is secure — vibration shortens battery life. Belts and Fluids Inspect the serpentine belt for cracks, glazing or fraying. A belt that fails takes the water pump, alternator and power steering with it. Check the tensioner for smooth operation and the idler pulleys for bearing noise. Check engine oil level and condition. Heat accelerates oil breakdown. Check transmission fluid where accessible. Towing in heat is hard on transmissions, and burnt fluid smells distinctly scorched. Check brake fluid. It absorbs moisture over time, which lowers its boiling point — relevant on long descents in hot weather. Brakes Summer brings mountain driving, towing and long descents, all of which generate serious brake heat. Check pad thickness and rotor condition before a long trip. Service the caliper slide pins so the caliper releases properly — a dragging brake generates heat continuously, which is far worse in summer. Note a soft or sinking pedal, which can indicate moisture in the brake fluid boiling under heat. Paint and Interior UV exposure does cumulative, irreversible damage. Wash and apply a wax or sealant. The protective layer matters more in summer than any other season. Park in shade where possible. This does more for paint longevity than any product. Carbon fiber parts are particularly vulnerable — UV yellows the clear coat and the resin beneath. A UV-protective sealant applied periodically genuinely extends their appearance. Use a windscreen shade to reduce interior temperatures and slow dashboard cracking. Clean and protect interior trim, which fades and becomes brittle under sustained UV. Before a Long Summer Trip Check all fluids and top up as needed. Verify tire pressures including the spare, and confirm you have the tools to change a wheel. Test the AC properly, not just briefly. Inspect the coolant system, since a long highway run in heat is where a marginal cooling system gives up. Carry water — for the occupants first, and useful if you do end up waiting for assistance. If the Temperature Gauge Climbs Switch off the air conditioning and turn the heater to maximum — the heater core acts as a secondary radiator and can buy you time. Pull over safely and shut the engine off. Do not open the radiator cap on a hot engine. The system is pressurised and the coolant is above its atmospheric boiling point; releasing that pressure causes it to flash to steam violently. Wait until it is genuinely cool. Continuing to drive an overheating engine risks a warped head, a failed head gasket, or worse. It is one of the few faults where stopping immediately is clearly the cheaper option.