what does white smoke from exhaust mean？
Under normal circumstances, the exhaust gas discharged from the exhaust pipe is generally colorless gas. However, if you notice that the car emits black smoke, white smoke, or blue smoke, it means that your engine has a problem. So the question is: why does my car smoke? What do these different smoke colors mean? Next, this article by Caleph Engineers will provide you with car exhaust smoke diagnosis.
What is exhaust pipe?
Exhaust system definition
Automobile exhaust system refers to the system that collects and discharges exhaust gas, which is generally composed of exhaust manifold, exhaust pipe, catalytic converter, exhaust temperature sensor, automobile muffler and exhaust tail pipe. The function of automobile exhaust system is mainly to discharge the exhaust gas generated during the combustion process of the engine. At the same time, it reduces the pollution of the exhaust gas, and is mainly used in light vehicles, micro cars and buses, motorcycles and other motor vehicles.
Exhaust system function
The function of the automobile exhaust system is to collect the exhaust gas from each engine cylinder, reduce the exhaust noise, eliminate the flames and sparks in the exhaust gas, discharge the exhaust gas safely into the atmosphere, and discharge harmful substances. The exhaust gas is controlled.
The main working principle of the exhaust system is to divert the airflow through multiple channels. These diversions will gradually reduce the flow rate of the airflow due to friction and collision with each other. This cycle is repeated, and finally the exhaust gas is discharged through the exhaust pipe of the car, which reduces the noise, thereby achieving the effect of reducing the noise of daily cars.
Types of Exhaust Smoke
White smoke from exhaust
The formation of white smoke
In the engine, if the diesel cannot be completely evaporated and burned, the unburned diesel oil droplets will form particles with water vapor and be discharged with the exhaust gas or the engine oil will be discharged directly from the exhaust pipe, forming “white smoke”.
Cause of failure
- Oil contaminated by water: Water leakage caused by damage to the cylinder gasket, cracked cylinder liner or cylinder head, etc. will cause water to enter the cylinder and contact the hot engine parts, turning into water vapor and being discharged from the engine through the exhaust system, forming white smoke.
- Delayed injection timing: Severe wear of the camshaft of the injection pump of individual cylinders will cause the cylinder injection time to lag too much, resulting in incomplete combustion of diesel in the cylinder, and unburned fuel will be discharged from the exhaust pipe in the form of white smoke.
- Poor atomization of the injector: The injector is responsible for spraying the fuel into the engine combustion chamber in the form of fine mist. If the injector cannot atomize the fuel normally or there is excess gasket under the injector nozzle, it will cause poor combustion and produce white smoke.
- Water-cooled intercooler leakage: The intercooler is used to cool the intake air after the turbocharger compresses the air. If the water-cooled intercooler leaks, the coolant will mix with the intake air and enter the cylinder, and the water in the intake air will turn into steam during the combustion process, producing white smoke.
- Low ambient temperature: When the temperature is too low, the cylinder temperature is difficult to rise, especially when the engine is just started in the morning, white smoke will be emitted. As the engine heats up, the smoke will turn into blue smoke and soon become colorless. This is a normal phenomenon and needs to be distinguished from the fault.
Solution to white smoke
Drain the water in the fuel tank or oil pipe, open the fuel tank drain valve, drain the water and sediment in the fuel tank until there is no water in the discharged oil. When replacing the injector, be sure to remove the copper gasket under the old injector and replace it with a new sealing ring to ensure normal sealing and injection performance.
After the engine runs for a period of time (preheating), the white smoke will automatically clear when the temperature reaches a certain level.
The injector drips oil, causing some diesel to be incompletely atomized in the combustion chamber. The solution is to repair or replace the injector.
If the cylinder gasket is damaged or the contact surface between the cylinder head and the cylinder block is uneven, the cylinder gasket or cylinder head should be replaced. When installing a new cylinder gasket, be sure to ensure that the contact surface between the cylinder head and the cylinder block is flat and undamaged to ensure a good seal.
Blue smoke from exhaust
The formation of blue smoke
- The intake valve oil seal is worn or damaged, resulting in a loose seal, and the oil enters the combustion chamber and burns.
- The piston ring loses its elasticity or breaks, or the cylinder liner is severely worn, and the oil leaks into the combustion chamber. This situation usually causes a large amount of exhaust gas to come out of the exhaust pipe.
- The seal ring at the impeller end of the supercharger compressor is not sealed tightly, and the oil enters the cylinder combustion chamber and burns.
Solution to blue smoke
Drain the excess oil in the oil pan, keep the oil level within the dipstick mark, and ensure that the oil is clean and free of debris.
If the oil ring inside the piston ring is stuck in the ring groove, the oil ring will lose its ability to scrape oil. Clean the carbon deposits in the ring groove and replace the piston ring if necessary.
If the piston ring is worn or damaged, the oil may enter the top of the cylinder from the gap between the piston ring and the cylinder liner and burn. The piston ring needs to be replaced.
If the cylinder liner is severely worn or the piston is damaged, the oil may leak into the combustion chamber. In this case, the piston and cylinder may need to be replaced or repaired.
If the valve guide is worn or damaged, the oil may leak into the cylinder combustion chamber from the gap between the valve guides. The valve guide should be repaired or replaced.
If there is too much oil in the air filter, it may be sucked into the cylinder and burned. The solution is to pour out some of the oil or replace the air filter to reduce the oil height of the air filter.
Black smoke from exhaust
The formation of black smoke
Black smoke is generally produced when the diesel generator set is under heavy load, such as full load or overload. Black smoke is the product of incomplete combustion. When the engine is under heavy load, the combustion chamber temperature is high, too much fuel is injected, the mixture is unevenly formed, and insufficient air is generated in local areas during combustion. The fuel is easily decomposed under high temperature and oxygen-deficient conditions and accumulates into black smoke.
Cause of failure
Before checking whether the exhaust pipe emits black smoke, the air filter should be removed first. If the black smoke in the exhaust pipe disappears, it means that the air filter is seriously blocked, resulting in insufficient air intake, causing black smoke. At the same time, check whether the intake pipe is blocked, such as the intake hose being sucked flat.
The injection time is too late, and the diesel cannot be completely burned in the cylinder. In the cold engine state, the exhaust pipe generally emits gray-white smoke, and black smoke when the engine temperature is normal. The correctness of the injection time not only causes black smoke from the exhaust pipe, but also has a great impact on the power and economy of the engine.
When the injector fails, the single cylinder oil cut-off method can be used to check the working condition of each cylinder. If the engine speed does not change significantly and the black smoke disappears after a cylinder is cut off from oil, it means that the cylinder is emitting black smoke due to poor spraying and oil dripping from the injector.
Excessive oil supply from the injection pump or uneven oil supply to each cylinder will also cause black smoke from the exhaust pipe, so the injection pump oil supply must be readjusted. Improper adjustment of the smoke limiter will also cause black smoke from the exhaust pipe.
Severe wear of the compressor impeller or turbine of the supercharger will reduce the intake volume and cause black smoke from the exhaust pipe. Severe leakage of the exhaust pipe gasket or supercharger interface gasket will also cause insufficient intake volume, black smoke from the exhaust pipe or reduced engine power.
Solution to black smoke
- Reduce the load to the approved range.
- Adjust the fuel supply advance angle. For a single cylinder, this can be achieved by adding or removing gaskets. For multiple cylinders, this can be adjusted on the test bench.
- Adjust the fuel supply volume. This can be achieved by changing the length of the governor cable.
- Clean the oil hole and adjust the fuel supply pressure. For multiple cylinders, this can be operated on the test bench.
- Insufficient cylinder compression force is caused by wear of the cylinder barrel, piston, valve and other parts. If necessary, they should be replaced in time.
- Check the air filter and muffler. If necessary, replace the air filter element and remove carbon deposits.
- Clean the diesel tank and oil pipeline and use diesel that meets the requirements.
Common Causes of Exhaust Smoke
Condensation
Condensation occurs when you start your engine in cold weather. It causes white smoke to come out of the exhaust pipe, which is normal and will go away if the exhaust system warms up as the car warms up. If the white smoke persists, it may indicate a coolant leak that requires immediate attention.
Oil Leaks
Oil leaks can cause blue or gray smoke. Oil leaks can be caused by problems such as worn or cracked valve seals or piston rings, which can cause oil to enter the combustion chamber and burn with the fuel, causing blue smoke to come out of the exhaust pipe and can cause engine damage if not treated.
Coolant Leaks
White smoke with a sweet smell indicates a coolant leak caused by a blown cylinder head gasket, a cracked engine block, or a faulty cylinder head. A coolant leak can cause serious engine problems if not repaired promptly.
Fuel System Issues
When there is a problem with the fuel system, black smoke will come out of the exhaust system. This indicates that too much fuel is being burned. This can be caused by a clogged air filter or a faulty fuel injector. In a diesel engine, this means that there is a buildup of soot and the diesel particulate filter needs to be cleaned.
Diagnosing Exhaust Smoke Issues
This is a question that many car owners are concerned about. When we encounter the phenomenon of exhaust pipe smoking, how can we judge whether it is normal? It can help us take corresponding measures in time to avoid greater losses. Here are some judgment methods:
Observe the duration and amount of smoke
If white smoke only appears when the vehicle starts, but as the car starts, the white smoke gradually dissipates, which means it is a normal phenomenon,
but if after a period of time, the white smoke continues to come out and spreads in the air, it means that there is a problem that needs to be dealt with.
Smell the smoke
If the smoke has no obvious smell, it means water vapor or water mist.
If the white smoke has a sweet or pungent smell, it means that the coolant is leaking.
If the smoke smells oily or burnt, it means that it is engine oil.
Look at the color of the smoke
Take a piece of white paper and place it near the exhaust pipe:
- If there is no obvious stain on the white paper, it means there is water vapor or water mist.
- If there are black or yellow stains on the white paper, it means it is engine oil.
- If the color on the white paper is orange or pink, it means it is coolant.
Observe the coolant pot and dipstick
- If the liquid level in the coolant pot is significantly lowered and there is foam or emulsification, it means that the coolant has entered the engine.
- If the oil on the dipstick becomes darker or thinner and there are water droplets or emulsification, it means that the oil has entered the cooling system.
The above judgment method can help the owner preliminarily diagnose the cause of exhaust pipe smoke, but it cannot determine the specific location and extent of the fault. Therefore, it is recommended that the owner go to a professional auto repair shop for inspection and repair in time when abnormal phenomena are found to avoid greater losses.
Preventing Exhaust Smoke Problems
In order to prevent the occurrence of exhaust pipe smoke failure, these methods can effectively protect the normal operation of the engine and exhaust system, improve the performance and life of the car, and reduce the maintenance costs and environmental pollution of the car. The following are some specific contents of the prevention and treatment methods:
Three no leaks
No oil leakage: Ensure that the gaskets of the low-pressure oil pipe and the high-pressure oil pipe are free of oil and keep them clean to effectively prevent damage caused by oil infiltration.
No air leakage: The hose connection of the air filter must not leak and must be kept sealed. Air leakage will destroy the air-fuel ratio of the engine, resulting in performance degradation and increased emissions.
No water leakage: The radiator, cylinder gasket or water plug must not leak water to ensure a good circulating water state. If water leakage is not handled in time, it will cause the generator to overheat and damage the engine.
Four cleanings
- Clean diesel: Each time you add diesel, it is best to add diesel that has been settled for more than 48 hours to ensure that there are no particulate debris in it. Clean and replace the diesel filter regularly to reduce the wear of the precision parts of the fuel system and extend its service life.
- Clean the engine oil: Replace the engine oil regularly. Choose the right engine oil according to the season to ensure lubrication. Replace the oil filter regularly to achieve the best lubrication and reduce component wear.
- Clean the air: To ensure smooth air circulation, it is necessary to clean the various components in the air filter regularly. At the same time, pay attention to the cleaning and replacement of the air filter. In harsh environments, consider using a high-flow air filter to minimize the inhalation of impurities such as dust to achieve good air filtration effects.
- Clean water:Use clean water in the radiator, such as distilled water or well-precipitated water. The water tank should not be short of water during operation to avoid poor heat dissipation leading to a decrease in engine power.
Conclusion
Identifying the color of exhaust smoke is crucial for car owners. White smoke is normal when starting, but if it persists, it may indicate a coolant leak. Blue or gray smoke indicates an oil leak, and black smoke indicates an overly rich fuel mixture or a fuel system malfunction. If abnormal smoke is present, a mechanic should be consulted immediately for repair. Caleph has more than a decade of experience in manufacturing automotive parts and can provide expertise. Regular inspections can improve the performance and life of your car.