1. There is too much oil in the oil pan.
The amount of oil in the oil pan is not necessarily the more the better. Adding too much oil to the engine oil pan not only causes significant resistance for the crankshaft during high-speed rotation but also causes a large amount of oil to splash onto the cylinder wall. A large quantity of oil enters the combustion chamber before being scraped off by the piston ring and participates in combustion, generating a lot of blue smoke and carbon deposits, accelerating component wear. Excessive oil can also lead to a reduction in the space within the crankcase or an increase in negative pressure in the oil chamber, causing the oil to rise up to the cylinder or resulting in leakage.
When checking the oil level in the oil pan, do not remove the oil dipstick while the engine just shut down. Because at this time, the oil that has splashed onto the walls of the crankcase and cylinder still has not completely returned to the oil pan, so you should stop the engine for 5 to 10 minutes before removing the dipstick to check the oil level and see if it meets the requirements. If there is too much oil, the oil drain plug should be opened to drain some of the oil to the specified liquid level.
2. The valves and valve guides are severely worn.
The valve guides of the engine play a role in guiding the opening and closing of the intake and exhaust valves. Severely worn valves and guides will cause an increase in the clearance between them, which will result in the lubricating oil for the valve rocker arms being sucked into the combustion chamber through the gap between the intake valve rod and the guide, and then participating in the combustion. Therefore, when inspecting and repairing the engine, special attention should be paid to the clearance between the valves and the guides. If it exceeds the specified technical indicators, they should be replaced.
For engines with oil seals attached to the tubes, prolonged use or substandard lubricants can cause the valve oil seals to age and deteriorate prematurely, thereby allowing some engine oil to pass through the damaged valve tube oil seals and enter the combustion chamber for combustion. Especially, the aging and damage of the intake valve oil seal make it more likely for engine oil to enter the combustion chamber. Therefore, when repairing the engine, the tube oil seals must be installed properly, and the valve rods must be able to slide freely within the tubes. During the engine's operation, it is necessary to use the specified lubricants as per the manual, choose the appropriate brand, and perform regular replacement and maintenance.
3. Excessive oil in the air filter
For engines equipped with oil bath type air filters, if there is too much oil in the oil pan inside the filter, when the engine is running at high speed, the excessive oil will pass through the intake pipe and enter the combustion chamber, participating in the combustion process, resulting in blue smoke emission from the engine and a large amount of carbon deposits. This will accelerate the engine's wear and affect its normal service life. Therefore, when adding clean oil to an engine with an oil bath type filter, one should pay attention to the oil level. Generally, it should be added to the middle position between the upper and lower marks, and do not add too much.
4. Turbocharger malfunction
For diesel engines with turbochargers, if the engine is burning oil, the exhaust pipe emits blue smoke, and the engine's power remains unchanged, and if there is oil contamination on the compressor side of the turbocharger's intake port or the intake hose, it can be determined that the floating bearing and sealing device on the compressor side of the turbocharger have been damaged, resulting in oil leakage.
The engine oil will be carried along with the airflow of the compressor in the turbocharger and enter the engine intake pipe, then be sucked into the combustion chamber to participate in the combustion, causing the engine to emit blue smoke. When the turbocharger malfunctions, it is necessary to repair it in time or replace the new part to ensure the normal operation of the engine, extend the maintenance period and reduce the usage cost.
5. The piston, piston ring, and cylinder liner are severely worn.
When the overly worn piston or cylinder liner is in operation, the clearance between them will increase significantly. This causes the oil splashed onto the cylinder wall to easily enter the combustion chamber and participate in the combustion process. At the same time, due to the poor sealing between the cylinder, the piston, and the piston ring, a large amount of exhaust gas is produced in the crankcase. As a result, the engine's power decreases significantly, and a large amount of blue smoke is emitted from the exhaust pipe. In such cases, the engine should be promptly inspected and repaired, or new parts should be replaced based on the wear condition of the piston and cylinder liner.
Overly worn piston rings not only cause the elasticity of the rings to decrease and lose their elastic sealing function, but also lead to ring breakage, which weakens the oil scraping and distribution functions of the oil rings. There is also a possibility of seizing the cylinder, resulting in a large amount of engine oil flowing into the combustion chamber for combustion, while emitting a large amount of blue smoke. Regarding this situation, when repairing and assembling piston rings, without replacing the piston, the carbon deposits on the old piston should be cleaned first. Then, each piston ring should be correctly installed at the specified assembly position (pay attention to the position and cutting direction of each ring during assembly, and the inner cutting surface should face the top of the piston). If necessary, new rings and new pistons should be replaced.
In conclusion, there are various reasons for oil burning in diesel engines. Therefore, in the future, during the use of the engine, timely maintenance and care should be carried out for the engine, attention should be paid to the working environment of the engine, the operation status of the engine should be observed, and appropriate fuel and lubricating oil should be selected according to the technical requirements of the engine. Regular inspections and maintenance should be carried out to effectively reduce the premature wear of various components of the engine, allowing the diesel engine to operate in a good condition and extending the service life of the engine.