The color of the exhaust gas: that's what the exhaust gases reveal!

Reading time 7 Min.

Recently updated on January 27, 2022 at 10:41 am

With the following article we would like to explain what the exhaust color reveals about the engine. It is not unusual for smoke to escape from the exhaust. But we've all seen it before when a car becomes one huge black cloud comes out of the exhaust. If the exhaust color looks different than "normal", then it can various causes to have. Some of these are very easy to fix; other causes may require one reorganization of the motor. We want to try to get to the bottom of the matter and provide information on what the color of car exhaust has to say about the condition of the engine.

What you should know about exhaust gases

If the engine is working well, the fuel is just going to be, so Diesel or gasoline burned. Combustion creates various combustion products that are blown out through the exhaust. This mixture of substances makes up the majority of the CO2, and it also contains nitrogen oxides, carbon monoxide and hydrocarbons. These substances are not really visible. So you can see that a mixture of condensation and the finest soot particles is escaping from the exhaust. The condensation water always occurs when hot gases meet cold gases. Incidentally, the contrails in the sky are also created in this way. If there are problems with the engine and it no longer runs smoothly, the composition of the gas mixture is changed and thus also changes the color of the exhaust.

Where does the water come from when white smoke is steaming out of the exhaust?

If it happens that White smoke escapes from the exhaust, it means that somewhere Water got into the exhaust gas. This can happen after you've parked the car on a cold day. As a result, condensation has collected in the pipe of the exhaust, which slowly evaporates due to the hot exhaust gases. This is nothing bad and it's not dangerous either. However, if you notice that after a few kilometers of driving, white fumes are still coming out of the exhaust, then it becomes a problem.

Circulate in the engine block three liquids and these are Coolant, Oil and fuel. To prevent these liquids from mixing with each other is the Cylinder head gasket installed. Should be the cylinder head gasket run away, then coolant can penetrate into the combustion chamber, as this consists mainly of water. In the combustion chamber, the coolant then evaporates and occurs in a more or less large white cloud out of the exhaust. In this case, take a look at cooling system provide answers.

Is the engine cold, then you can safely open the lid of the container. Fill in water and start the engine. Should Coolant bubbles can be seen, it is probably due to the cylinder head gasket. But here we have good news for you: Do not move the car, as this can cause such a defect still to be fixed. Now comes some not so good news, unfortunately this venture is right expensive and also takes some time as it is more or less costly at a hunt.

more information about the white smoke from the exhaust:

• Exhaust gases from the internal combustion engine mainly consist of nitrogen (N2), carbon dioxide (CO₂) and water vapor (H₂O)
• white smoke usually indicates that water is evaporating (this can be for a number of reasons)
• What to look out for?
  - Does the white smoke only appear after a cold start and / or on cold days?
  - does the problem also exist when the engine is warm?
  - are they very large clouds of smoke or rather small ones?
• consider unusually much white smoke should the engine as quickly as possible be turned off
• Is it maybe just evaporating condensation water?
  - Is the smoke only after the start and / or on cold days? Then evaporating condensation water within the exhaust system is often the problem.
  - evaporating condensation water is in the form of smoke or smoke unproblematic and disappears again after a short time.
• Cylinder head gasket / cylinder head defective
  - If the white smoke remains after a few kilometers of driving, then a defective cylinder head gasket or a defective cylinder head may be the problem (Cooling water enters the combustion chamber and evaporates)
  - This also leads to restrictions in the cooling or lubrication of the engine and in the worst case can result in engine damage.
• approx. cost of changing the cylinder head gasket / changing the cylinder head

  Material / service	Exchange cylinder head gasket	Exchange cylinder head
  Material costs	100 to 500 euros	500 to 1.800 euros
  Labor costs (100 € hours)	200 to 900 euros	200 to 1.000 euros
  Motor oil including oil filter	30 to 180 euros	30 to 180 euros
  cooling water	20 to 75 euros	20 to 75 euros

  total cost	around 350 to 1.750 euros	around 800 to 3.200 euros

• defective turbocharger
  - Oil can get into the turbocharger, where it is compressed and burned
  - Depending on the severity, this leads to thick, white clouds of smoke that smell strongly of oil

  Material / service	Prices for a new part
  turbocharger	600 to 3.000 euros
  Labor costs (100 € hours)	200 to 1.000 euros
  Engine oil & oil filter	30 to 180 euros
  total cost	around 850 to 4.200 euros

• General inspection with white exhaust smoke?
  - if the exhaust gas values ​​are increased as a result, there is a significant deficiency
  - The main inspection is then not passed

black smoke: illegal tuning or real problem

Rolling Coal, Black smoke from the exhaust, now it's going to be American! We know this from the USA, where it is well known that it is almost a national sport. With us, however, it is frowned upon and is even more difficult Fine punished. If you while driving thick and black smoke notice at the same time no If you have installed an illegal rolling coal system, then there is a problem with the spark, Lambda probe or the Motor Control of the car. It's a sign that something incomplete burns. It arise Fuel residuesoot and come out of the exhaust. The result is a thick, black cloud of smoke.

Tip: more information, in case of "black smoke"

Fortunately, however, these are common problems that occur more often and are usually easy to fix. An appointment in a workshop is, however essentialbecause the electronic systems of modern cars, which are known to be quite complex, cannot be inspected and repaired in the home parking lot.

What if blue smoke comes out of the exhaust?

The blue smoke it is important to take a closer look at the matter. What does the color look like exactly? Is it more of a light blue? Then it could be a sign of another problem with similar causes. In this case it is Engine oil (instead of water), which gets into the combustion chambers. Blue smoke poses no immediate danger to the car, but in the worst case scenario, the real problem could be engine failure have as a consequence. For example, if you accidentally too much oil have filled in, one can still speak of luck.

Tip: more information if there is “blue smoke”

The pressure in the oil system then increases and the lubricant presses against the cylinder rings into the combustion chamber, which causes the blue smoke. A simple one oil change or at least sucking off the excess amount is the key to happiness here. Is it just one minimal amount, then maybe this amount is enough to be burned.

If the oil level is back to normal, but the smoke is still blue, then there may be other causes that favor the blue smoke. Keyword: Cylinder head gasket! Look for the coolant and oil. Pay attention to the liquid in the coolant reservoir. If there is a milky, light brown liquid or the oil is frothy, this is an indication of one broken seal. The coolant, the oil and of course the seal must then exchanged .

We stay on the subject of "leaks". When a Cylinder ring is defective or the Valve stem seal is porous, oil also gets into the combustion chambers. Such defects can cannot be diagnosed alone. The problem can be solved in a professional workshop with the appropriate equipment, as special tools are almost always required.

And finally ... Unfortunately, it is commonplace that many vehicles are on the road with the exhaust emissions described above. This should to be taken seriously, because eye-catching exhaust colors - especially if they are permanent - are symptoms of serious problemsthat can even lead to a total write-off. Also maybe completely different things like a defective turbocharger, a broken oil cooler, a defective one Heat-exchanger or a broken one Air flow sensor affect the color of the exhaust gas. Our contribution has only shown "some" of the possibilities. That's why we advise attentiveness with changing exhaust colors. Don't be afraid to seek advice from a professional. You will definitely have a trustworthy workshop near you that will get to the bottom of the problem.

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