White smoke from the exhaust
Thick white smoke from the exhaust pipe can be alarming for drivers due to its volume and strong smell. In many cases, it is just water vapour in cold weather, but thick white smoke that doesn't disappear after the engine warms up signals serious engine trouble.
Likely causes — most common first
Blown head gasket
A damaged gasket allows coolant (antifreeze) to leak into the engine cylinders, where it burns and turns into thick white vapour.
Cracked engine block or cylinder head
A crack in the metal allows coolant to leak into the combustion chamber constantly, even once the engine is fully warmed up.
Normal water vapour and condensation
In cold or damp weather, moisture builds up on the exhaust system walls and evaporates during startup and the first few miles of driving.
Fuel system fault (injectors)
If fuel is being delivered incorrectly or not burning completely in the cylinders, it can cause thick light or grey smoke with a strong smell of diesel or petrol.
