What Does the Smoke from My Exhaust Mean: blue, white, grey, black?


The condition and health of the engine of your car is heavily reliant on the type and color of emissions that it produces. Normally, a good engine will not emit noticeable emissions except in extreme cold weather conditions when they will mix with water vapor to produce a white gas. This is not a cause for alarm. If smokes is visible from your car’s exhaust, there may be a problem developing under the hood of your car. Immediate action to address it is recommended to prevent more problems from developing. However, you can effectively diagnose the problem with your engine by considering the color of the emissions. Here are the four different color emissions that you are likely to see from your exhaust and what they mean.

1. Blue Smoke from exhaust

Usually, if your car produces clear blue smoke everything should been fine. However if the emissions are dark blue and have been produced over a long period time, there may be a problem with your engine. The problem is normally the leakage and burning of oil meant for lubricating your engine.

According to AutoGuide.com, if your piston rings or valve guides are worn out, oil is bound to leak into the combustion chamber. It mixes with gas/petrol in the chamber and are burnt together thereby resulting in the production of the blue emissions.

To solve and prevent this from happening, you are advised to regularly check the status of the oil in your car. Also ensure to check the plugs and valves just in case they are loose and require replacement. If the leakage of oil into the chamber is not dealt with, it causes rough engine-starts and it may spoil your spark plugs or starter and cost you more money.

Is your car Turbo-charged and still emitting blue smoke even after dealing with the above problem? Turbo-charged vehicles will normally emit blue smoke if the blower and turbo-charger need replacement.

2. White Smoke from exhaust

Sometimes, white emissions from your vehicle may just be the condensed vapor from inside your exhaust and which is not a cause for alarm. On the other hand if your car produces thick white smoke and over a long period of time, there may be a problem.

Cause of white smoke from exhaust

The head gasket may be blown. According to procarmechanics.com, the structure of your engine is divided into the engine block and a cylinder head. The block houses the coolant passageways and cylinders. A head gasket is used to seal the block and the cylinder head. If the loose, compromised or damaged, coolant from the passageways may leak into the combustion chamber and get burned with gas/petrol. This will lead to the emission of white fumes.

Engine over-heat. Due to the leakage of the coolant into the combustion chamber, your car is deprived off a significant amount of coolant and will eventually lead to overheating of the engine. Don’t wait for the engine light to blink on your dash-board to confirm this. White smoke is usually the first signs of an overheating engine.

Damaged cylinder head. The cylinder head houses the combustion chamber. Most of the explosive aspects of your vehicle will take place here. A crack or tear on the cylinder head may also lead to the leakage of the coolant into the chamber which causes white emissions. A damaged cylinder head is a serious problem that may require a complete replacement. In the long-run, a damaged cylinder head may force you to consider a new car.

Cracked engine block. This is a critical condition and in many cases, it is irreparable. As stated earlier, the block supports and houses almost all the components of your vehicles engine. It is built with strong durable metal like aluminum or iron. A crack on the block can cause massive leakages making your car emit dark white fumes. An engine replacement is the only better option is such cases.

To solve and prevent white fumes emission from your car, always ensure regular check-up on the block, cylinders, gasket and passageway areas. Also be sure to have the head gasket replaced and regularly checked for any faults. Remember not to overfill your car with coolant which may lead to leakage.

3. Grey smoke from exhaust

Like blue smoke, grey smoke will usually be an indication of oil leakage and combustion in your car’s combustion chamber. This also applies to turbo-charged vehicles in need of blower replacement. Precautions taken when blue smoke is seen will apply if the emission color is gray.

The emission of grey smoke may also have the following indications;

Transmission fluid leakage. Fluid used by your vehicles transmission may be leaking and mixing with gas/petrol in the combustion chamber. This is mostly caused by the transmission vacuum modulator if it is faulty or lose, which causes leakage.

Faulty valve stem seals. Oil is used to lubricate the valve guides in the combustion chamber. The valve stems are used to regulate the amount of oil applied to its interface to lubricate the guides in the chamber. If the stem seals are loose or faulty, oil may be leaking into the chamber, which them produces grey emissions.

Stuck Positive Crankcase Ventilation (PCV) valve. Your car comprises a PCV system whose purpose is to recycle emissions into the combustion chamber, mostly those that are not properly burnt. The valve may get stuck or lose and lead to oil leakage into the chamber causing grey fumes.

To solve/prevent grey emissions from your vehicle, be sure to check the valve stem seals and replace any faulty ones. Also check out for any leakages of the transmission fluid and oil.

4. Black smoke from exhaust

The most common cause of black emissions is the burning of excessive fuel in your engine. This means too much gas/petrol is getting into the combustion chamber but not all of it is being burnt. To prevent this be sure to fill your tank with enough gas and not too much. Other reasons why your car may be producing black smoke is;

Dirty air-filter. The air filter is meant to allow oxygen into the chamber for combustion and prevent substances from getting into the chamber. If it is clogged, lesser air is allowed into the chamber, resulting in your car burning too much fuel with a limited supply of oxygen which causes black smoke.

Faulty fuel pressure regulator. The regulator controls the pressure with which your car runs on. If it is faulty, it may cause a fluctuation of the required pressure, which in turn may limit the amount of fuel reaching the combustion chamber. This will cause poor combustion, a rough engine start and visible black smoke.

Clogged fuel injectors. These are used to spray the required amount of fuel meant to mix with the oxygen to start your engine. If the fuel injectors are faulty or clogged, too much fuel may be leaking into the chamber with a limited supply of oxygen. This will in turn cause the production of black fumes.

To stop/prevent your car from emitting black fuels ensure to check and clean the air filters and fuel injectors and replace any faulty ones.

Many drivers will usually wait until they see the engine light or a red light on the dash-board before they take any action. The truth is, the red light will normally come at the end when immense damage has been done. Early signs of engine problems like emissions can help you solve the problem under the hood faster and at a cheaper cost. Be sure to keep an eye on what your car emits and make regular check-ups to your mechanic.

Below YouTube video for a more detailed explanation on the kind of smoke your car is emitting and what it means.

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