What does White Smoke from the Car Exhaust Mean?

What does White Smoke from the Car Exhaust Mean?

Your exhaust pipe is one of the most important ways to determine the health of your car. Exhaust fumes are an unfortunate necessity of the internal combustion engine. They are a byproduct of the fuel being burned to propel the car. If smoke is being released, then this is indicative of a problem. There are different types of smoke which may be emitted and it's possible you might ask what does white smoke from the car exhaust mean? oneHOWTO looks at all the possible reasons why white smoke is coming from your exhaust pipe. We'll also look at the different types of smoke and how they can reveal specific problems.

White smoke from the exhaust on startup

When the white smoke comes out of your exhaust can help us to know what is causing the problem. If white smoke comes out when the ignition is started there are a few reasons. The first one is an internal problem which we will discuss further below.

Another important factor is the type of engine of your car. If your car has a diesel engine, then the white smoke might be indicating that there is a problem with the fuel pump injection. When the fuel pump injection timing is off, it is difficult to determine the root cause. There are two main reasons, the first might be dirty or low quality fuel (something which can be problematic with diesel engines). The second will be a mechanical problem.

Unfortunately, these problems are often difficult to diagnose at home. You can check your fuel pump injection timing yourself, but replacing the parts will be something a professional mechanic will need to take care of.

If you see white smoke coming out of the car exhaust pipe in thin wisps, but only when you start the engine and not while driving, there should be no need to worry. This is due to an accumulation of condensation that finds its way out through the exhaust pipe. When you start the engine, the wispy white ‘smoke’ isn't smoke at all, but the vapor going into the air due to the heat.

White smoke when the car is running

If white smoke continues to come out of your exhaust while the car is running, there are other issues at fault. One cause of white smoke from the exhaust might be the engine leaking coolant. If the engine leaks coolant, it will be burned by the heat of the engine and then come out as smoke from the exhaust.

A problem with antifreeze might also be causing white smoke to come from the exhaust. Antifreeze is used to stop your car from seizing up in cold weather. If it is leaking in your engine, then it may get into the cylinder where the fuel is burned to make the car move. The exhaust takes smoke from the cylinders and removes it form the engine system, so the white smoke is the result of a material being burned which shouldn't be.

Another problem with antifreeze is if it runs out. This means the engine might be overheating and the result is white smoke from the tailpipe. Head gaskets are there to prevent things which shouldn't entering the cylinders. If the engine overheats due to a lack of antifreeze or coolant, then the gaskets fail to work properly. This can allow other things to enter into the cylinders such as outside pollution, dirt, sand or whatever if in the environment.

You will need to check the antifreeze and coolant. If it needs replacing, then do it. However, if the damage is done, then you will need to take the car to a mechanic for engine repair. his could involve replacing the gaskets. If the car is getting too hot, then you should know what to do if your car overheats.

Gaskets sealing the cylinders aren't the only possible leakage. Piston rings malfunctioning or worn out can also lead to leakage which, in turn, leads to white smoke from the tailpipe.

White smoke depending on thickness

Thin smoke

White smoke coming from the back of your car can be ignored if it is thin like vapor. This is probably coming because of normal condensation build-up in your car’s exhaust system, especially if it has undergone damp or cold climate conditions. It is normal, nothing to be concerned about, and will disappear quickly.

If you haven't used your car for a while, then once you start it up again thin smoke may come out if you haven't recently re-filled the gas or added any fuel stabilizer. In this case, we advise you to add some fuel stabilizer or to drain the old gas and re-fill it with fresh gas.

Thick smoke

But if the smoke is thick, it can be a big problem. It may be caused because the engine is burning coolant. This may be due to a serious issue, like blown head gasket, damaged cylinder head or cracked engine block. These are costly repairs, and need to be attended to immediately. Even small leaks in the coolant may lead to overheating, and cause serious damage to your car’s engine. Coolant may also end up mixing with the oil, and thus causing serious damage to your beloved vehicle.

If you use the wrong fuel in your car, then smoke will come out of the exhaust. White smoke might happen if you use unleaded when you should use leaded or vice versa. However, if you put diesel in a gas engine, then thick smoke will come out immediately and your engine will splutter to a stop. In this case, some white smoke is the least of your worries.

Fuel filter related problems

The fact that the car is emitting a lot of white smoke from the exhaust when it's already running can be a sign of more serious and costly problems, and it should be repaired as soon as possible. The smoke could indicate more serious problems with the fuel filter, cylinder head, the cylinder head gasket or even a crack in the engine block. Keep in mind that problems of this kind can be quite costly.

What to do when your car is emitting white smoke

If you see white smoke coming from your car’s exhaust make sure you follow this procedure:

  1. Stop the car immediately and check and make sure that there is a proper amount of anti-freeze in your car’s radiator, change it if needed and also the over-flow bottle.
  2. Also check if anti-freeze has contaminated your car’s engine oil. You can check the engine oil dipstick, and also the under-side of the engine oil filler cap. If you see contamination with anti-freeze, which will look like a chocolate milkshake, you should not start your engine, and contact a mechanic as soon as possible.
  3. If you continue driving your car with contaminated oil, it may cause serious damage to your car’s engine, which will end up in extremely costly repairs and replacements.

Now you know the reasons, take a look at how to stop white smoke from the exhaust, you'll find solutions no matter what the underlying cause is. You can also take a look at the reasons for black smoke coming from the exhaust.

If you regularly keep up with the maintenance of your car, you can detect these problems early, before they become expensive or even impossible to repair.

If you want to read similar articles to What does White Smoke from the Car Exhaust Mean?, we recommend you visit our Car Maintenance and Repair category.

  • Do not overlook the problem if white smoke is coming out of your exhaust as it could be a serious issue for both your car and other drivers on the road.