Drivers Urged to Wait 15 Minutes Before Starting Cars in Heatwave

As temperatures in the United Kingdom soar into the 30s Celsius this week, drivers are being advised to exercise caution when starting their vehicles. According to automotive expert Kazimieras Urbonas, starting a car during peak afternoon heat could lead to serious engine damage and costly repairs. The fourth heatwave of the summer has prompted amber health warnings, emphasizing the need for drivers to be mindful of their vehicle’s well-being.

During peak heat hours, typically between 11:00 and 15:00, the temperature inside a car can significantly exceed the outside air temperature. This creates a hazardous environment for vehicle engines, which can lead to mechanical failures if not handled properly. Urbonas, who serves as a Supplier Excellence Manager at Ovoko, one of Europe’s largest online marketplaces for used car parts, has witnessed the detrimental effects of extreme heat on vehicles firsthand.

“Most drivers don’t realize that their car’s engine bay can reach temperatures far higher than the outside air temperature during a heatwave,” Urbonas explained. “When you try to start a superheated engine, you’re asking it to work even harder when it’s already under incredible stress.”

The issue begins well before the ignition key is turned. Throughout the hot day, heat accumulates under the bonnet, effectively transforming the engine bay into an oven. By late afternoon, when temperatures peak, the metal components become superheated and struggle to function correctly. Engine bay temperatures can rise by 20-30 degrees Celsius compared to outside temperatures.

Starting a vehicle that has been exposed to intense heat — such as 34°C — forces an already stressed engine to generate even more heat through combustion. “The cooling system becomes overwhelmed,” Urbonas noted. “Your radiator and cooling fans are working overtime just to maintain normal temperatures, but they’re fighting a losing battle against the ambient heat.”

The repercussions of starting a superheated engine can be severe. Not only does it strain the cooling system, but it can also cause expensive internal damage that may not become apparent until it is too late. Under extreme heat, metal components expand differently, and sudden temperature changes from starting the engine can lead to warping.

Urbonas highlighted that during heatwave periods, many damaged parts, such as cylinder heads, gaskets, and cooling system components, appear in the marketplace. “These repairs aren’t cheap — we’re talking hundreds or even thousands of pounds,” he stated. The most vulnerable parts include rubber seals and gaskets, which can fail under extreme temperatures, resulting in coolant leaks and engine overheating.

To help drivers navigate these conditions, Urbonas identified key warning signs that indicate an engine is struggling with the heat. “Even if it’s not in the red zone, a higher-than-usual reading during startup is a clear warning sign,” he advised. Additionally, if drivers detect a sweet smell from coolant or observe steam when opening the bonnet, their cooling system is already under severe stress. Unusual noises, such as pinging or knocking, may also signify that engine components are expanding beyond their normal tolerances.

To mitigate the risks associated with extreme heat, Urbonas recommends waiting 15-20 minutes after peak heat hours before starting a vehicle. “If you must drive during peak heat, start the car and let it idle for a minute or two before driving off,” he suggested. This allows the cooling system a chance to circulate before the engine is put under load.

Prevention is key when it comes to engine protection during heatwaves. Simple steps, such as parking in shaded areas, using reflective windscreen covers, and regularly checking coolant levels, can save drivers significant amounts of money and stress.

“Regular maintenance becomes even more important during hot weather,” Urbonas emphasized. “Ensure your cooling system is in top condition: check for leaks, make sure your radiator is clean, and consider having your coolant changed if it’s been a while. A well-maintained cooling system is your first line of defense against heat damage.”

If drivers notice any warning signs, Urbonas advises against ignoring them. “The cost of a simple coolant top-up or radiator flush is negligible compared to replacing a warped cylinder head or blown gasket,” he concluded. “At Ovoko, we see too many expensive failures that could have been prevented with basic precautions and early intervention.”