As you know, the internal combustion engine consists of a large number of loaded parts and assemblies. For normal operation of the mating surfaces (friction pairs) it is necessary to supply lubricant to such surfaces. Engine oil in the engine serves to protect, lubricate, cool and remove wear products.
Normally, the oil that lubricates the various elements of the internal combustion engine should not enter the combustion chamber in excess. In other words, in a serviceable engine, only a slight penetration of lubricant into the combustion chamber of the engine is allowed. However, during operation of the power unit, various deviations and breakdowns often occur.
Malfunctions lead to the fact that the oil begins to be consumed intensively, the ignition system malfunctions (spark plugs in oil), the combustion chamber becomes contaminated with oil, the engine cokes, etc. Next we will talk about why the lubricant ends up in the engine cylinder and the plugs are filled with oil, as well as what the cause of such a malfunction may be.
Why engine oil gets into the combustion chamber
So, the driver may find that the spark plugs are in the oil, the engine smokes blue smoke, increased oil consumption, as well as the power unit starts worse, it can trottle, somewhat loses engine power, etc.
Not surprisingly, the lubrication in the combustion chamber negatively affects the operation of the internal combustion engine. If otherwise, engine oil loss (in the engine cylinder lubricating fluid is burned at the moment when the fuel-air mixture is burned in the cylinder) not only requires constant monitoring of the level and refilling of the lubricating fluid, but also gradually puts the engine out of operation.
It is quite obvious that this problem should be solved as soon as possible to avoid more serious consequences. Now let’s consider why oil gets into the combustion chamber.
First of all, a sure sign of such a malfunction is the presence of oil on the spark plugs. Simply put, in the case when the electrodes are greased, this indicates that the oiling of the plugs directly indicates excessive penetration of lubricant into the engine cylinder.
As for the causes, in the list of the main specialists distinguish the following:
- there are problems with valve guides or valve seals;
- the valves themselves are defective;
- laid or worn out piston rings;
- the engine is allowed overflow of engine oil;
- there are problems with the ventilation of the boat;
Let’s look at these faults in order. As a rule, the wear of the inner surface of the valve guides leads to a strong backlash between the valve stem and the guide sleeve. As a result, oil from the cylinder-head enters the combustion chamber and greases the spark plugs.
Less often the problem area is the valve guide sleeve, which comes out of the cylinder head body. Usually this situation occurs if the guides have been previously changed, but put not repair increased size, but standard.
If we talk about valve glands, these parts are made of rubber. Over time, the gland hardens, loses elasticity and begins to leak oil into the cylinders. Overheating of the internal combustion engine can also quickly destroy valve seals.
In the list of symptoms indicating problems with valve seals, the presence of oil on the thread of the spark plug is noted, as well as the appearance of blue oily exhaust on a cold engine. At the same time, after warming up the engine, the intensity of smoke decreases or completely disappears.
In addition to the loss of elasticity of oil seals, it is quite possible that the crimp spring has been stretched, the spring can jump off the body of the oil seal, etc. It can also happen that the gland “breaks away” from the guide bushing. If the sleeve is worn out, the valve works in such a way that only one side is pressed down. As a result, the lip of the packing is bent away, allowing oil to enter the combustion chamber.
It is for this reason that it is not advisable to replace the oil caps in case of severe wear of the valve sleeves or valve stems. The fact is that even new valve packing will not be able to work properly and will quickly fail, that is, the oil consumption after repair will not fall.
We should also note that the valves themselves also wear out. If we talk about the oil in the cylinders, then the problem is associated with the valve stem. The wear of the rod leads to the fact that there is an increased gap between the guide and the valve stem. Oil in this case through the leakage “flows” into the cylinder. In order to effectively solve the problem, it is necessary to replace the valves, and in many cases also the valve guide sleeves.
As for cylinders and pistons, in this case, during the movement of the piston, friction occurs between the cylinder wall and the piston rings. The piston rings are mounted on the piston and are necessary to seal the gaps between the piston and the cylinder walls.
In order to achieve lubrication and at the same time avoid oil getting into the combustion chamber, a so-called oil ring is placed on the piston, which “removes” lubricant from the cylinder wall when the piston moves. If the rings are worn out or there are defects in the cylinder mirror, then the engine oil is literally drawn into the combustion chamber.
Signs of problems with the rings are the accumulation of engine oil on the threads of the spark plugs, as well as on the insulator. To more accurately determine the fault, it is recommended to measure the compression in the engine cylinders. If the compression is low, in this situation, one possible solution is to replace the piston rings. The pistons themselves are also quite often changed, as they may well crack the partitions under the rings.
High oil level in the engine occurs both after overfilling of lubrication, and in the case of antifreeze/tosol or a large amount of fuel getting into the oil system. If it is a case of normal over level, then the excess oil from the engine should be pumped out.
In case fuel or antifreeze gets into the oil system, the engine needs urgent repair. It is important to realize that both coolant and fuel have an extremely negative effect on the properties of the lubricant. This means that the engine with such a malfunction can not be further operated, as there is a high probability of its severe wear and even jamming.
The crankcase ventilation system normally neutralizes the accumulation of crankcase gases and normalizes the crankcase pressure. If the ventilation system does not work properly, the pressure rises, which causes oil to enter the combustion chamber.
As a result, the piston rings cannot “remove” the excess oil from the cylinder walls, lubricant gets into the combustion chamber, oiling of the plugs occurs, etc.
What the result is
As you can see, oil in the engine cylinders can appear for various reasons. In this case, in all cases, there is an increase in the consumption of lubricant, there is blue smoke from the exhaust pipe, and also the presence of lubricant on the spark plugs is noted.
We should add that usually the plugs, filled with oil, become the cause of a difficult start of the internal combustion engine, ignition skips and engine trojan. Oil in this situation has to be constantly refilled, the plugs need cleaning or frequent replacement, and such actions still do not solve the main problem.
It is important to realize that there should not be excess oil in the combustion chamber. Otherwise, the engine will be subjected to increased wear, the combustion chamber becomes contaminated, valve seats and plates, as well as elements of the CPG suffer. For this reason, it is necessary to timely identify and eliminate the cause of oil in the engine cylinder.