What are the main reasons for white smoke from the engine?

[Ellen]

The main reasons for white smoke from the engine are: 1. The engine temperature is too low, causing some diesel fuel to turn into oil vapor without burning and being discharged with the exhaust gas from the exhaust pipe; 2. There is water in the fuel supply system, either in the fuel or the combustion chamber. The water is heated by the combustion heat in the cylinder into steam, which is discharged from the exhaust pipe, forming white smoke; 3. The fuel injection timing is too late. Due to the delayed injection, the cylinder temperature has already dropped when fuel is injected, causing some diesel fuel to turn into oil vapor without burning; 4. Poor atomization of the fuel injector. Inadequate atomization leads to incomplete combustion of diesel fuel, which combines with the high-temperature exhaust gas from normally operating cylinders in the exhaust pipe, resulting in white smoke; 5. The cylinder pressure is too low, causing some diesel fuel to turn into oil vapor without burning, thus emitting white smoke from the exhaust pipe.

[VonAiden]

Engine emitting white smoke is quite common, and I've encountered it several times myself. It's mainly caused by coolant leaking into the combustion chamber, such as due to a damaged cylinder head gasket or cracks in the cylinder head. When these components age, they may leak coolant, which turns into steam and comes out of the exhaust pipe during combustion. Another possibility is during rainy or snowy weather when water enters the engine, causing excessive water vapor. Additionally, in diesel engines, if the fuel contains impurities or water, it can also produce white smoke during combustion. I must say, this isn't a minor issue; if not repaired promptly, it could lead to more serious failures, such as engine overheating and complete breakdown. I recommend first checking if the coolant level has dropped. If it's low, you should take it to a professional shop for inspection. For prevention, regular maintenance of the cooling system and fuel filter is key, which can save you a lot of money.

[LaStella]

Excessive white smoke from the engine is often related to water, and I've thought about this issue. Cooling system problems are the main culprits, such as leaks from damaged gaskets or caps allowing water into the cylinders, which then produces large amounts of white smoke during combustion. For diesel vehicles, low-quality fuel containing moisture can also cause this. It's important to distinguish normal conditions—some steam during cold starts is normal, but if it persists or is accompanied by a sweet smell, be alert. Don't overlook checking the battery or voltage issues, as low voltage can sometimes cause system abnormalities. From experience, DIY checks are too risky; it's better to touch the exhaust pipe after parking—if it's wet and has an unusual odor, get it repaired immediately. Long-term neglect not only wastes fuel but can also reduce engine lifespan by more than half. I make it a habit to conduct a comprehensive inspection every six months.

[SophieFitz]

I think the most common cause of white smoke is water or coolant entering the engine. Normally, it's just water vapor, but in a faulty state, it could be due to damaged gaskets, coolant leaks, or impurities in the fuel. This can easily be misdiagnosed, so pay attention to the color and smell of the smoke; a sweet smell indicates coolant mixing in, while an oil-like smell means burning oil. Don't rush to repair the car; first, simply check the coolant level yourself. If it's low, top it up and see. Remember, safety first—if this happens on the highway, slow down and pull over. Prevention relies on regular maintenance, so check related components when changing the oil.