What to do if an emulsion appears on the oil filler cap

Specialists in car maintenance, as well as automakers recommend changing the oil in gasoline or every 10 thousand kilometers. But even if you comply with this regulation, sooner or later the car owner notices that an emulsion has formed on the oil filler cap. In appearance, this emulsion resembles mayonnaise and plunges many drivers, especially beginners, into shock. By the way, the color of "mayonnaise" may vary. Let's look at the causes of this phenomenon, and also find out how to deal with the problem.

What is a white emulsion?

Modern engine oils, which are sold today everywhere and everywhere, are made on a hydrocarbon basis. During the combustion of gasoline various substances are formed. These are antifreeze, water, alcohols, acids, and also peroxides. All these substances in the hydrocarbons are mixed, resulting in a white emulsion on the oil filler cap.Why does it appear exactly here? It's simple - because of the huge number of microscopic bubbles, the emulsion has a white color in case of severe contamination of the oil. The filler cap and dipstick is one of the coldest places.emulsion on the oil filler capTherefore, “mayonnaise” sticks well to these surfaces.


Specialists in car maintenance and just experienced motorists say that there are a lot of reasons for the appearance of an emulsion. Most often, this white mixture can occur when coolant enters the crankcase of the power unit. This can happen due to the breakdown of the gasket between the cylinder head and the engine block. Also, the emulsion on the oil filler cap may indicate cracks in the cylinder block or in the head. Another possible reason for antifreeze getting into the crankcase is the deformation of the cylinder head elements. Condensation may still occur, especially in winter.white emulsion on the oil filler capAlso "mayonnaise" is formed when there is no ventilation of crankcase gases in the engine. The gas is hot, and it contains a large amount of water, which is deposited in the form of condensate at the top of the engine. As a result, a white emulsion accumulates on the lid.oil filler cap. Finding out the exact reason why this frightening many mayonnaise motorists is quite difficult. But in most cases this is due to the breakdown of the cylinder head gasket. Because of this, the coolant easily gets into the oil channels and there it is mixed with oil. It should be noted that if antifreeze got into the lubricant, it is no longer subject to operation. Both oil and coolant must be replaced. This is true for all models of cars. An emulsion appears on the oil filler cap on any and all machines, if there is damage or operating conditions are violated. Often, motorists are faced with "mayonnaise" of different colors at the first temperature drops - in the fall and winter. But do not sound the alarm. This condensate arises due to the temperature difference between the heated engine and the air outside. When the motor is warm, then the moisture in the oil will evaporate, but some of it will accumulate in the form of condensate on the stopper. What is interesting: many cars are subject to this disease, but the "Gazelle" practically does not suffer from it.

Possible consequences

When water, condensate or coolant enters the lubricants, the oil quickly loses its properties. Accordingly, lubricating properties are reduced. In winter, oils can even crystallize, which will not affect the operation of the engine in the best way. The film between the friction pairs of parts leads to rapid wear of all the parts in the motor.cause emulsion cap oil filler capMost often in these cases, the engine simply wedges, and this is an expensive repair. Therefore, if an emulsion has formed on the oil filler cap, the reasons should be carefully examined. It is urgent to find the fault and fix it.

About condensate more

Such a problem is faced even by those who store their cars in the garage. But most often it worries those who put the car in the yard. If the car regularly spends the night on the street in the fall during the rainy season, then a large amount of water vapor may well get into the crankcase cavity. They condense in pipes and on oily surfaces. At one time in the motor can get from 1-2 g of condensate. This is enough to form an emulsion on the oil filler cap. By the way, bubbles will be visible on the dipstick.In winter, the owner will see “mayonnaise” very often. If the car constantly travels short distances and the motor does not warm up to 90 degrees, then this is also one of the reasons why condensate accumulates in the engine. "Treatment" is made by long runs, or by warming up to operating temperatures.

Faulty crankcase ventilation system

If the ventilation system is clogged and does not work as it should, then gases and vapors will try to exit through the probe and other places in the engine. In this case, it is not surprising that an emulsion appeared on the oil filler cap.yellow emulsion on the oil filler capThe only good news is that the oil is clean and does not have antifreeze. If you correct the ventilation system of crankcase gases, then you do not even have to replace the lubricants.

Coolant: a serious case

It is necessary to consider this topic in more detail. One of the most common sources of liquids that, when mixed with oil, form an emulsion is antifreeze, or antifreeze. Why does it happen and how does the coolant get into the engine? It's simple. The coolant gets through damage in the area of ​​the cylinder head gasket from the cooling circuits.Antifreeze penetrates there under great pressure. This is normal, because it is much less in half a butter.


To check these causes, the lubricant is drained from a sufficiently heated engine to a previously prepared container. In the hot oil, even with the naked eye, there will be traces of coolant, which, as it cools, will turn into an emulsion. If there is a lot of water in the antifreeze, then most of it will accumulate under the layer at the bottom of the crankcase. Naturally, this oil will suck up the oil receiver. If a yellow emulsion has formed on the oil filler cap, then it is better to temporarily abandon the operation of the vehicle. A viscous mixture will clog channels for lubrication. Connecting rod bearings, piston rings, main bearings with such a liquid will quickly fail.

Bad fuel as one of the reasons

If the oil contains an emulsion, it is a consequence of the fact that the car was filled with low-quality gasoline.an emulsion appeared on the oil filler capToday, kerosene, alcohol, water and other ingredients will sometimes contain fuel. Conclusion - in order to eliminate the formation of "mayonnaise" in the engine, it is better to refuel at proven gas stations.

Breakdown of the cylinder head gasket

If the emulsion is visible on the oil filler cap, the reasons are often a violation of the gasket tightness. Breakdown is possible due to burnout due to overheating or as a result of physical obsolescence and wear of the gasket. But such cases are found only on old engines, which are not followed. The main symptom of a breakdown is the unstable operation of the motor. There will also be noticeable withdrawal of coolant from the expansion tank. If you perform diagnostics in a timely manner, then you can limit yourself to just replacing the gasket. This is done in just two hours. If you let go of the situation, then everything will be much worse.

Cracks in the cylinder head and block

The emulsion on the oil filler cap (VAZ-2107 including) is often formed due to cracks in the head or block. This happens because of antifreeze freezing. It is necessary to monitor the performance characteristics of coolant. Do not pour water into the radiator.emulsion on the lid of the oil filler neck of the VAZIt remains inside the system even then, if you completely drain the coolant. As a result, water freezes in the most inappropriate places. Most often the channels of the block or cylinder head crack. Also, the engine is deformed due to mechanical shock.If there was a frontal hit in the car, do not exclude the possibility of cracks on the block.

Water in the engine tray

This problem can be solved only by completely replacing the lubricant. It is best to flush the engine using specialized substances. An emulsion is often formed on the cap of the oil filler cap in winter due to temperature fluctuations.emulsion on the oil filler cap condensateThe situation when water enters the crankcase through the combustion chambers is very rare in itself. This is only possible on motors where the piston group is in poor condition with “tired” rings.


As you can see, “mayonnaise” is a bad sign for a motor. It is important to constantly monitor the state of the power unit. If time does not fix the problem, you can get to expensive repairs. At the first sign, when an emulsion forms on the oil filler cap (condensate or not, it does not matter), you must immediately take the necessary measures.

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