Causes of oil escape through the breather plug

In the process of combustion of working mixtures in the engine cylinders there is a buildup of exhaust gases, which are under high pressure. Pressure causes some of the gases to leak into the crankcase. There they mix with oil vapors and condensation water. The resulting gas mixture is called crankcase gases.

As the pressure increases, the gas mixture bursts through the following elements:

If there is a characteristic effect called “oil flowing” it means that there is engine oil involved when the gases are exhausted. To stop the moving oil from the diesel engine breather, it is necessary to maintain the pressure inside the engine within acceptable limits by venting the crankcase gases through the ventilation system.

How it works

Why does oil leak and squeeze out of the breather plug?? To answer this question, let’s understand. How the breather works, and why it spits oil. As many people know, gases collect in the crater of the engine during operation. A special ventilation system, called a breather valve, is used to bleed oil. This helps relieve the pressure inside the engine. Since there is always a suspension of air and fine oil droplets in the crankcase, it is not surprising that some of the lubricant flows with the air into the breather.

There’s an oil-collecting strainer. But, some of the droplets are still flying around. So, a little contamination (near the end of the operation) of the air filter is quite normal. When oil becomes too much, it makes sense to look for the cause.

Crankcase ventilation system malfunction

In the rhythm of the engine’s work, during acceleration, off-road driving, the combustion fuel-air mixture creates pressure that is much higher than usual. The amount of gas that escapes through the piston rings into the engine oil sump will be considerably higher. A properly functioning sump vent allows the gases to flow freely to the intercooler and then to the combustion chambers with the fuel-air mixture. Due to the fact that the oil catcher performance is gradually deteriorating, as well as valve springs, the pressure in the sump increases, causing the exhaust gases to start dripping oil into the intercooler.

After cooling down, the oil that has got into the intercooler accumulates at the bottom of the radiator. In addition, the oil begins to lose its properties, so that the lubrication of the turbine deteriorates, traces of wear are formed on the shaft. Another negative moment, which is fraught with poor functioning of this system. a decrease in engine power and an increase in fuel consumption. Due to the fact that the flow of air throws oil into the intercooler, and from there it enters the cylinders, changes the mode of combustion.

How to install the piston rings on the engine of a power tiller

Blue puffs of smoke when your power tiller is running and excessive oil and fuel consumption indicate that the piston rings have failed. To replace the piston rings on a power tiller engine yourself, you will need the following tool:

To replace the piston rings, you must first dismantle the block heads and the oil pump. Then the cylinder should be thoroughly cleaned from the layer of carbon deposits that have formed on its surface. The next step is to insert the upper ring 5 mm into the cylinder and measure the gap (use a feeler gauge for this). Then the ring should be placed to a depth of 11 mm in the area where there is excessive wear on the cylinder, and make the appropriate measurements. If the indicators of wear is less than 0.17 mm, in this case it is necessary to carry out its replacement.

Thanks to the replacement of piston rings there is a restoration of compression indicators, and reduces fuel consumption. In addition, in most cases, after replacing the rings, extraneous noise that occurs during the operation of the engine disappears.


It is much more important to find out why the engine is running oil through the breather, because this will make it possible to find the cause and eliminate it. It makes no difference whether this is done by yourself or with the help of specialists.

Interestingly, some reasons may not directly relate to the ventilation system at all.

Among the main causes of oil in the breather note the following:

  • Severely worn piston rings and cylinder heads. This causes a large volume of gases to leak into the crankcase and the regular ventilation system has no time to deal with them. Increased pressure in the internal combustion chamber and squeezing of the oil through the breather valve.
  • Drainage channel of oil separator clogged over time. As a result, the separated oil has no other way but to mix with the passing gases.
  • Problems with the air filter. Or to be more precise, its contamination. When the engine is running, it needs a large volume of air. If the filter gets clogged, the engine feels the lack of air, and starts sucking it in from other available sources. This is mainly the ventilation system.
  • Excessive volume of oil in the system. The common mistake of beginners, who change oil for the first time by themselves and pour more than required. The surplus ends up in the vent.
  • Jammed valve. The breather valve itself, i.e. the breather valve, can jam. It ceases to perform its functions fully. Hence the oil.
  • Worn timing or burned-out valve. This can allow gas from the crankcase to enter the space above the valve. It then enters the crankcase, pressure builds up, and oil squeezes out.

As you can see, you should not blame the breather plug for all the troubles at once.

Diagnose leakage of lubricant

To identify the causes of the defect of the lubricant flow through the diesel and turbo diesel breather, it is necessary to carry out a comprehensive inspection of the power unit. This does not require disassembly of the engine. Experienced craftsmen measure certain parameters and visually assess the condition of the elements that make up the ventilation system.

At detection of plaque and oil deposits in the intake manifold the conclusion about the presence of lubricant through the diesel breather seals is made. For diagnostics you need a set of tools, consisting of an open-end wrench, screwdrivers, compression gauge.

  • Exhaust gases analysis. switch on the engine and check the color of the exhaust. The black or blue hue indicates that oil is leaking into the cylinders, i.e. there is wear, tear, or oil leakage in the cylinder. ะบ. the oil ring is worn, and there are problems with the camshaft mechanism.
  • Check compression in each cylinder. The value of compression equal to 11. 13 MPa indicates the proper operation of the cylinders and pistons. The difference between the compression in the cylinders should not exceed one Megapascal. The engine oil pressure is too low in one cylinder and can cause leakage of lubricant.
  • Locate the exact cause of the piston ring defect with a glow plug. The plug is removed and checked for the presence of strong traces of carbon deposits, which indicate defects in the cylinder. piston group.
  • No soot on the spark plug indicates that it is necessary to check the valves.
  • If compression in all cylinders is normal, further inspection and cleaning of ventilation system components is required.All input devices are to be dismantled and thoroughly rinsed, dried and then re-installed.

Vent design features, operating principle

The simplest crankcase ventilation circuitry used on internal combustion engines previously consisted of only one connection. the crankcase breather.

This breather connected the internal chamber of the cylinder block with the external environment and the crankcase gases simply flowed out through it into the atmosphere.

But such a scheme had a major drawback. the exhaust gases contained oil particles, which also got into the environment. And it is not only losses of lubricant and the need in its refilling from time to time, but also contamination of the atmosphere.

On modern cars, the ventilation system is closed. It also has a breather pipe, but a branch pipe is connected to this to allow the gases to flow into the intake manifold or air cleaner housing where they enter the cylinders and are burned. So they don’t pollute the atmosphere.

In addition, the system includes elements that ensure separation of oil and return it back into the crankcase, so that it does not get into the cylinders with the gases.

There are several versions of oil separators, and in cars of different manufacturers they may differ in design and operating principle.

It is worth noting that some of the exhaust gases get into the over-valve space, and they also need to be drained.

Therefore, the entire scheme of the engine ventilation system on a modern car consists of a breather, oil separator and two pipes.

Additionally, the system can include a special valve that regulates the pressure of gases entering the intake manifold.

The system may be configured in many ways, but this does not change its function or principle. For example, consider the construction of ventilation VAZ-2110.

reason, escape, breather

In the lower part of the cylinder block of the car installed breather pipe, on which the other end of the hose through the fitting connected to the cylinder head cap. The oil separator is located inside the air intake nozzle.

There is another nozzle on its other side to which the pipe to the intake air stub pipe is connected.

The principle of operation of such ventilation is simple. the gases enter the cylinder head space through the breather and pass through the oil separator, with the separated oil flowing to the valve assembly.

The gases then mix with those that have burst into the over-valve space and flow into the air pipe and then into the manifold. There is no pressure regulating valve in this car.

READER’S POWERFUL: What is the current leak in cars, how to measure it?

On other cars, the oil separator may be located right next to the breather valve and the valve is installed behind it.

Carrying out diagnostics of lubricant escape

To identify the causes of the defect of the lubricant flow through the diesel and turbo diesel breather, it is necessary to conduct a comprehensive inspection of the power unit. It does not require disassembly of the engine. Experienced craftsmen measure certain parameters and visually assess the condition of the elements that make up the ventilation system.

At detection of plaque and oil deposits in the intake manifold the conclusion is made about the presence of lubricant escape through the diesel breather gaskets. For diagnostics set of tools, consisting of open-end wrenches, screwdrivers, compression gauge is required.

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