A mechanic has urged drivers to stop driving immediately if they encounter a troublesome warning sign when behind the wheel.
Whilst drivers are more likely to notice smoke coming from the exhaust when they start their car in cold weather, the AA warned that white smoke could be a sign that there is a serious fault with the vehicle.
In particular, Shaun Jones, AA Patrol of the Year, noted that white smoke could suggest that the engine’s head gasket has blown due to a leak in the coolant system.
He advised: “If you notice white smoke coming from your car’s exhaust, it’s best not to continue driving. While short drives may be safe if the smoke is due to condensation, other causes, like a blown head gasket or coolant leaks, can worsen with driving.
“If there’s a coolant leak, it’s important to locate and repair the source, whether it’s the radiator, water pump, or worn seals.”
A head gasket is a seal between the cylinder head and block that prevents oil and coolant from mixing and helps boost power. It is found in almost all modern petrol and diesel engines.
If there is a coolant leak, the head gasket may fail – causing the engine to quickly overheat and a significant drop in power. If a driver continues to use the vehicle, components will not be properly lubricated, meaning they face a much higher risk of breakdowns.
As a result, it is vital that drivers who think their head gasket may be failing to get it checked by a mechanic, with the average cost to replace the part standing at around £700.
However, white exhaust smoke may also be a sign that coolant is leaking from another part of the car, with the AA suggesting it could also indicate a cracked cylinder head.
Located at the top of the engine, the cylinder head helps to control how much air and fuel each cylinder receives to get the best mix of power and fuel economy. If it cracks, coolant could leak into the component, resulting in white smoke from the exhaust.
In most cases, a cracked cylinder head will need to be completely replaced, which could cost between £600 and £1,000 depending on the engine.
Finally, Shaun suggested that drivers who encounter blue smoke also get their car checked quickly, with the symptom suggesting that the engine is burning too much oil.
He added: “For blue smoke, it’s important to act quickly. Avoid driving, as continuing to drive can worsen the problem, leading to more damage and costly repairs. You may also experience reduced fuel efficiency and engine performance issues.
“Blue smoke will cause your car to fail an MOT test and might violate emissions laws. It’s best to get your car checked by a mechanic as soon as you notice the smoke to prevent further damage. If concerned, consider breakdown cover for professional assistance and car maintenance advice.”
