What causes a diesel engine to smoke

Exhaust color: This is what the exhaust gases from the engine reveal

  1. What should I know about exhaust fumes?
  2. White smoke from the exhaust: where does the water come from?
  3. Black smoke from the exhaust: rolling coal?
  4. Blue smoke from the exhaust: how to find the problem
  5. Conclusion

What should I know about exhaust fumes?

A well-functioning engine will only burn gasoline or diesel. Different ones arise in the process Combustion productswhich are then released into the environment through the exhaust pipe. Most of this mixture of substances does that CO2 off, but also Hydrocarbons, nitrogen oxides and carbon monoxide can be found in it. None of these substances are really clearly visible. So what you see coming out of the exhaust is a mixture of the finest soot particles and condensation. The latter occurs when hot gases meet colder ones. The contrails in the sky are also created in this way. However, if the engine no longer runs so smoothly, the composition of the emitted mixture often changes, and with it the color of the exhaust gas.

White smoke from the exhaust: where does the water come from?

White smoke from the exhaust suggests that somewhere Water in the exhaust gas got. This can happen in the exhaust if, for example, the car was parked on a cold day. Then condensation water collects in the exhaust pipe, which slowly evaporates through the hot exhaust gases. That is not a problem at all and not dangerous. But if white fumes are still oozing from the exhaust after a few miles, the engine has a more serious problem.

Three different fluids circulate in an engine block: fuel, oil and coolant. The cylinder head gasket is designed to keep these fluids from mixing. If it burns out, coolant, which consists largely of water, can penetrate the combustion chamber. There it evaporates and emerges from the exhaust in thick, white plumes. A check of the cooling system provides information: When the engine is cold, you can open the lid of the coolant tank, top up with water and start the engine. If you see bubbles in the coolant now, the most likely cause is the cylinder head gasket. The good news: if you stop driving your car, you can usually fix such a defect. The bad news: It could be expensive and time-consuming.

Exhaust gas recirculation - this is how you reduce pollutant emissions!

Black smoke from the exhaust: rolling coal?

What some of the less socially competent Americans have elevated to a national sport can not only be punishing looks in this country, but also one hefty fine broken in. Who fat while driving black smoke secretes, either has one Problem with the car's oxygen sensor, spark plugs, or engine control. Black smoke is caused by incomplete combustion. Fuel residue clogs up and emerges from the exhaust. The black smoke is the result. Fortunately, most of the time, such mistakes are real Routine problems and therefore easily resolved. A visit to the workshop will still have to be made, because the complex electronic systems that are in a modern car cannot be serviced in the driveway at home.

Blue smoke from the exhaust: how to find the problem

If your exhaust is smoking white it may be worth looking closely. Is the smoke a light blue after all? This is an indication of another problem, but it can have similar causes. This time it's not the water, it's Engine oil that gets into the combustion chambers. The blue exhaust itself is not very dangerous for your car, the basic one However, the problem can cause major engine damage. You are lucky if you accidentally too much oil have filled. Then the pressure in the oil system rises and the lubricant is pushed past the cylinder rings into the combustion chamber, where it burns to light blue smoke. An oil change can help here.

If the oil level is okay, there are a few other things that can cause the blue smoke. First of all, the reason may again be the Cylinder head gasket be. Check the oil and coolant. If you see a light brown, milky liquid in the coolant reservoir or if the oil is frothy, this is it Broken seal. Then both the oil and the coolant and of course the seal have to be replaced.

And it continues leaking: A defective cylinder ring or a porous valve stem seal also lets oil get into the combustion chambers. However, these defects cannot be diagnosed without the help of a professional workshop. Special tools are required for this.


Unfortunately, you still see far too many cars on the road with emissions problems. Please keep in mind: Unusual exhaust colors are symptoms of serious problems which, in the worst case, can lead to a total loss. Therefore, please be vigilant if the exhaust color changes and use the service of a professional. Your trusted auto repair shop will help you solve the problem.

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