Under normal conditions, smoke comes out of your exhaust tailpipe.

Internal combustion engines burn a mixture of air and petrol to move the car. The afterburner gases consist of hydrocarbons that are harmful to the environment. The catalytic converter uses a catalytic process to remove the harmful gases, leaving carbon dioxide and water behind.

But in some moments – especially with old cars – you will notice thick white smoke from the engine compartment. This can be a sign of serious engine trouble and you should have your engine checked immediately. This article examines some common causes of white smoke from the engine.

Common causes of white smoke from the engine

On cooler days it is normal to see some white smoke coming from the engine. Internal combustion engines work by igniting the air-fuel mixture and produce carbon dioxide and water as byproducts. Very little smoke is expected due to the condensation of water from the exhaust gases. Furthermore, condensation occurs on the heated engine parts.

This is visible early in the morning, but if it continues throughout the day, you should call your mechanic for further investigation. The ignition moves the pistons up and down in the combustion chamber, which in turn moves the crankshaft and sets the car in motion. The engine gets hot over time and the coolant kicks in to cool it down.

The air-fuel mixture should never mix with the engine oil or coolant. If the coolant mixes with the oil, it will come out through the exhaust as white smoke. You can distinguish it from normal white smoke by its sweet smell. The thing to watch out for is excessive amounts of white smoke.

1. Coolant leaks

When coolant is heated, it produces white smoke. The most common cause of white smoke from the engine compartment is a coolant leak that occurs on a heated part such as the exhaust manifold. Open the hood and check for coolant leakage.

Remember that the coolant gets hotter than 90 degrees and you should be very careful when checking.

2. Overheating coolant

If your vehicle overheats, it forces coolant out of the coolant tank, which comes into contact with hot parts and condenses, producing white smoke. Check your temperature gauge to make sure it is not overheated.

3. Serpentine belt

Serpentine Belt

A defective serpentine belt can also cause white smoke in the engine compartment. This is often noticed with the smell of burning rubber. Check the serpentine belt and make sure that it is properly tensioned. A worn serpentine belt often also causes a loud squeezing noise.

Also, check the alternator and make sure that you can turn it freely after releasing the serpentine belt.

4. Bad valve cover

A bad valve cover causes engine oil to leak into the exhaust manifold. If this is the case, you will also notice a strong smell of burnt oil. Check whether oil is leaking around the valve cover gasket.

5. Other oil leaks

Check for oil leaks around the engine block to see if you can locate any leaks. Check the oil filter gasket and the oil lines located on the top of the engine.

In rare cases, there may be a crack in the engine block that pushes oil out. The engine block is made of strong materials and it is difficult for it to crack. But there are cases where you might have a cracked engine that is leaking oil or coolant. When this happens, you will notice white smoke from the engine compartment

How to fix the white smoke coming from the engine

The first thing you need to do whenever there is white smoke is to locate the problem: is it from the coolant or from an oil leak?

Leaking coolant is the primary cause of white smoke leaking from the engine. The cooling system flows from the radiator to the engine block. Start by checking the coolant level in the radiator. Do not attempt to open the radiator cap while the engine is still hot. When the engine has cooled, check the coolant tank and radiator hose lines for signs of leaks.

The engine emits different types of exhaust smoke – white, black, gray, and blue. For an accurate diagnosis, you must identify each one. If the exhaust emits black smoke, it means that the fuel has flooded the combustion chambers and is not fully ignited. You must check for clogged fuel filters, faulty fuel injectors, and sensors.

If you notice a strong smell together with the white-grey smoke from the engine compartment, it is most likely an oil leak.


It is normal for the vehicle to emit white smoke when starting in the morning or during the cold season. The catalyst converts the hydrocarbon gases in the exhaust system into carbon dioxide and water. This water often condenses in the muffler and exhaust pipes.

When you start the car, the engine heats up and these water droplets are emitted as white smoke. However, if the white smoke persists, this could mean that coolant is escaping into the combustion chambers. A damaged cylinder head gasket or a cracked engine block will cause coolant to escape.

White smoke, accompanied by a sweet smell, indicates that oil is leaking into the cylinders. You must check the piston rings for wear. The thickness of the smoke determines how serious the problem is.