Why does the engine exhaust blow blue smoke? 

If you have noticed blue smoke coming out of your exhaust, your car is experiencing a problem that needs attention. Regardless of the cause, blue smoke is always a signal that your car is burning oil. The reason this happens is because of worn or broken engine parts, such as piston rings or valve guide seals which causes oil to leak. The oil then flows into the combustion chamber where the oil and fuel burn together, causing the smoke blowing out of the engine exhaust to turn blue. This smoke takes on a foul smell and should not be breathed in.

An engine exhaust blowing blue smoke.

You may notice your car blowing other unusual colors of smoke. If that is the case, you can see some of the reasons why here.

What causes the engine exhaust to blow blue smoke? 

There are many reasons why engine components may be worn, which means there are many reasons your car might be blowing blue smoke. Blue smoke may occur when the car is starting or when the car is accelerating; each way signals to a different variety of possible issues. 

Blue smoke when starting:

Bad Valve Seals: If your car has been sitting for awhile and is not a diesel, you can probably bet the problem is with the car’s valve seals. Simply put, the valve seals are used to prevent oil from entering the engine. If they have been worn or broken, the valve stem seal oil can seep in and cause the oil and fuel to mix, creating blue smoke. 

Damaged Glow Plug: A glow plug is a component in diesel vehicles. They are used to ignite diesel fuel. If a diesel engine has a bad glow plug, when the car starts up it will create blue smoke until it has warmed up.

Blue smoke when accelerating:
Blue smoke that occurs when accelerating can have a few more causes. 

Stuck PVC Valve: The PCV valves’ purpose is to release pressure into the place where the engine gets its air for running, which is called the intake manifold. The intake manifold is connected to the air filter of your engine. So, if the PCV Valve gets stuck, oil, air and other gases will mix inside the engine. The burning of these different gases together will cause blue smoke.

Worn Engine: Specifically, the piston rings or cylinder of the engine getting worn out can cause blue smoke to blow out of the exhaust. The pistons move up and down a cylinder, and each piston has metal rings around it, called piston rings. The piston rings form a tight seal against the cylinder that blocks out oil, so if the rings or cylinder is worn out, oil from below the piston will come up. The oil then mixes with air and gasoline and again burns causing the blue smoke.

Blown Turbo: If your car has turbo, this is a likely cause of blue smoke coming out of the exhaust. If this is the case, the smoke will appear suddenly in a big cloud. A blown turbo caused by either damaged casing or a broken oil seal inside the turbo. Both causes let oil into the intake of the engine.

Transmission Fluid Loss: To shift transmission in older vehicles, a modulator is used with vacuum controlled automatic transmissions. Problems with the vacuum modulator, such as a failed diaphragm, causes the engine to suck in transmission fluid. The transmission fluid will then be burnt like oil, creating the blue smoke coming out of exhaust. 

What happens if blue exhaust smoke does not get fixed?

Because burning oil is likely a sign of damaged internal engine components, it is best to get it repaired as soon as possible. If the oil leak is not resolved, oil will continue to be consumed which can be potentially dangerous and cause major damage to your car’s engine, your health and the environment. Depending on the cause, different dangers can arise. The engine can begin to run rough if the oil is not burning properly in the cylinders, or spark plugs can become fouled by oil causing your check engine light to turn on to name a couple of examples. 

Generally, excessive oil in the exhaust can cause your catalytic converter to overheat or fail (which is a very expensive repair often over $1000). Also, if the oil continues to burn, low engine oil can result in a blown motor or seized engine.

Engine Exhaust Blowing Blue Smoke Repair in Hamilton 

Is blue smoke coming from your exhaust? If so, we can help!

Our team of experienced and skilled mechanics are able to quickly diagnose exhaust-related issues. We can then provide you with a detailed explanation and price estimate of what is wrong with your vehicle. If you choose to go forward with repairing the problem, we will provide high-quality repairs that you can rely on.

For exhaust diagnostics and repairs in Hamilton, contact Grimmer Motors today!


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