Drivers Advised to Avoid Engine Start During Peak Heat This Week

As temperatures in the UK soar into the 30s Celsius this week, motorists are being urged to exercise caution regarding their vehicles. With the fourth heatwave of the summer prompting amber health alerts, experts warn that starting a car during peak afternoon heat—typically between 11:00 and 15:00—could lead to significant engine damage and costly repairs.

Kazimieras Urbonas, a car expert and Supplier Excellence Manager at Ovoko, one of Europe’s largest online marketplaces for used car parts, highlights the risks associated with operating a vehicle in extreme heat. “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 states. Igniting a superheated engine subjects it to additional stress, potentially resulting in mechanical failure.

Understanding the Risks of Heat on Engine Performance

The primary concern begins long before the ignition key is turned. As the day progresses, heat accumulates under the car’s bonnet, effectively turning it into an oven. By late afternoon, when outside temperatures peak, the metal components within the engine are already struggling with the intense heat. On a typical summer day, the temperature inside the engine bay can rise by 20 to 30 degrees Celsius compared to the ambient temperature.

“Starting a car that has been sitting in 34C heat for hours means asking an already overheated system to generate even more heat through combustion,” Urbonas explains. This overwhelming heat can cause the cooling system to become ineffective, with the radiator and cooling fans working overtime to maintain appropriate temperatures.

The damage caused by starting an overheated engine may not be immediately visible. Metal components expand at different rates under extreme heat, and the abrupt temperature change from starting can lead to warping and other internal damage. “We see numerous damaged parts during heatwave periods,” Urbonas notes, mentioning that cylinder heads, gaskets, and cooling system components often fail due to heat stress. Repair costs for these issues can range from hundreds to thousands of pounds.

Recognizing Warning Signs of Engine Stress

Urbonas emphasizes several warning indicators that drivers should be mindful of during heatwaves. A higher-than-normal temperature reading during ignition is a clear sign of potential trouble. Additionally, if drivers smell sweet coolant or notice steam upon opening the bonnet, it indicates that the cooling system is under severe stress. Unusual noises, such as pinging or knocking, and a lack of responsiveness during acceleration may also suggest that engine parts are expanding beyond their normal limits.

To mitigate these risks, Urbonas advocates for a simple yet effective strategy: “Wait 15 to 20 minutes after peak heat hours before starting your car, or take steps to cool it down first.” If driving during peak temperatures is unavoidable, he recommends starting the car and allowing it to idle for a minute or two before setting off. This allows the cooling system to stabilize before the engine is put under load.

Preventative measures can significantly reduce the likelihood of costly repairs. Urbonas advises drivers to park in shaded areas whenever possible, use reflective windscreen covers, and check coolant levels before anticipated heatwaves. Regular maintenance is especially crucial during hot weather; ensuring that the cooling system is functioning properly can be a driver’s best defense against heat-related damage.

“If you notice any warning signs, do not ignore them,” Urbonas stresses. The cost of a simple coolant top-up or radiator flush is minimal compared to that of replacing a warped cylinder head or a blown gasket. At Ovoko, Urbonas and his team see too many expensive failures that could have been prevented with straightforward precautions and timely interventions.