17 Ways to Detect a Problem by the Colour of Your Car’s Exhaust Smoke


Sep 03rd, 2021

17 Ways to Detect a Problem by the Colour of Your Car’s Exhaust Smoke

Do you know that you can detect potential problems in your car solely by observing the exhaust smoke colour emitted by your vehicle? 

Yes, that’s true. 

17 Ways to Predict Potential Issues by the Colour of the Exhaust Smoke

Let’s cover some ways by which you can figure out the potential problems in your car.

White Smoke from Exhaust

White colour is the water vapour formed when the engine releases heat through the exhaust system. The water residing in the engine and or exhaust system gets vaporised and released through your car's exhaust pipe. Although there’s no need to worry about the white smoke from the exhaust in the cold weather, still here’s a list of what your car might be trying to say:

  1. If excess white smoke is being released, there’s probably a fault with your head gasket. Perhaps it’s failing or has completely failed.
  2. It could be an engine that’s too cold. Maybe you've parked your car in a very cool place, or maybe the water entered through the exhaust pipe when you washed the car.
  3. White smoke also indicates improper fuel burning in diesel engines.
  4. In the case of diesel engines, it can indicate a faulty injection system.
  5. Sometimes, white smoke is caused by an engine that’s starting to overheat.
  6. It could also be due to incorrect timing.
  7. For gasoline engines, it could be due to cracks or damage in the block or cylinder.

If you're using your car for short journeys, you might experience white smoke most of the time. That's because the vehicle couldn't warm up enough to vaporise all the water residing in the engine and or exhaust system. Driving the car for a long time should eliminate the white smoke. But if it doesn't, it surely demands immediate attention.

Blue Exhaust Smoke

  1. Blue smoke can result from oil leaking in the combustion chamber of a gasoline engine.
  2. Worn-out piston rings will cause blue smoke.
  3. Old valves or cylinders are the real culprit behind blue smoke.
  4. Diesel engine cars with high level of engine oil can also cause blue smoke.

Grey or Black Exhaust Smoke

  1. Oil leakage can cause grey or black exhaust smoke to be emitted. If the problem is severe, you’ll notice dense smoke as if something’s burning.
  2. A misbehaving fuel injector or a faulty injection system can also cause grey or black exhaust smoke.
  3. A clogged air filter forces the engine to produce black/grey smoke.
  4. If you use fuel of incorrect grade in your diesel car, black or grey smoke will be emitted.
  5. Improper timing can also cause smoke.
  6. An overheating engine will first produce grey smoke from the exhaust, but when the engine becomes extremely hot, the smoke can turn to black.

In some cases, taking the car for a long drive initiates the air filter to clean up automatically. However, there's no guarantee of success in this experiment, so please try it at your own risk.

Additional Diagnosis Tips

In addition to the ways for diagnosing problems as mentioned above, here’s a short and simple list of what you should exactly look for in your car. That'll give you a deeper insight into the actual problem. Here’s what to do:

  • Always check when smoke comes out and take note of the colour. For instance, if there's black smoke from the exhaust when accelerating or blue smoke from the exhaust when accelerating, there's a different set of potential issues compared to when the smoke is emitted during stable speed.
  • Observe the smoke’s density and see whether it’s dense, thick, or average. Dense smoke is a more severe sign of fault than thin smoke.
  • You should also observe how long it takes for the smoke to dissolve in the atmosphere. Thick smoke takes longer to dissolve in the air than thin smoke because of high levels of unsaturated or dense particles in it.
  • Try to figure out the type of smell of the smoke.
  • In case of black smoke, you should check if it's forming a trail on the road or there’s any saturation on your car's exhaust tip when the vehicle is parked.
  • When you see blue smoke from the exhaust when accelerating, it could be due to oil getting into the combustion chamber and burning with the fuel. This happens when your engine's valve seals are leaking. Merely getting the seals changed can fix the problem, but it's better to have a deeper inspection done by the mechanic.
  • Similarly, when you notice black smoke from the exhaust when accelerating, it means that your car’s engine can’t burn the fuel completely. If this problem worsens, you'll notice black trails on the road, highly dense black smoke from the exhaust, black saturation on your car's exhaust tip, and more. As a result, your fuel economy might degrade, forcing the engine to increase fuel consumption.

Is Smoke Colour an Accurate Indicator of a Car Problem?

Sometimes, smoke colour can also be a false alarm. If your car is properly maintained and serviced regularly on time, then colourful smoke isn't a big deal, and you can ignore it. However, if the problem persists for a long time, there's never harm in self-diagnosis. If you believe there's a problem, do not delay reaching out to a skilled mechanic.