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Diagnosing Car Exhaust Smoke

The quickest way to check any car engine is to give a close look at the car exhaust system through its tail pipe. In ideal condition you should not be able to see or feel the car smoke from the exhaust tail pipe, unless it's a diesel engine car that result in black smoke (normal). All petrol engine cars since last 10-15 years have been optimized to the extreme to not to pollute the environment. This resulting in most modern engines are getting very efficient and with all the current rules and regulations relating to environmental pollution, they will produce little to no smoke at all. Smoke from your exhaust can be one of the signs that your cars engine is having problems but what does it mean? Let's look at it here in more detail:


Black smoke

Black smoke indicates a rich air/fuel mix, i.e. too much fuel in the mix and not enough oxygen to burn it all. Some of the most common problems that can causes black smoke from car exhaust are:

  1. Dirty/blocked air filter
  2. Faulty temperature sensor 
  3. Injector/s stuck open
  4. Blocked fuel return line to tank
  5. Faulty FPR (Fuel Pressure Regulator)


White smoke

White smoke is steam, caused by water/coolant entering the combustion chamber. This can be caused by:

  1. Faulty head gasket
  2. Cracked cylinder head
  3. Cracked engine block
  4. Problem with turbocharger (Only water cooled turbos)


Blue smoke

Blue smoke is caused by oil entering the combustion chamber. This can be caused by:

  1. Worn valve stem oil seals
  2. Worn piston rings
  3. Worn cylinder walls
  4. Worn turbo seals
  5. PCV (Positive Crankcase Ventilation) valve stuck open


Here are the few videos to help you identify the colour of your car exhaust smoke:





**DISCLAIMER** I accept no responsibility for any misdiagnosis of exhaust smoke, this is just a simple guide on some of the possible causes. Always consult a qualified mechanic and read the workshop manual for your car before attempting any repairs.

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