What to do if your car is leaking oil through the breather

Oil squirting through the breather plug

The breather valve is also called the car breather valve, or a breather. The purpose of the device is to equalize the pressure created in the crankcase, in relation to the pressure from the outside. The need for equalization arises when the mechanism cools or, conversely, excessively heats up – as well as when changes in atmospheric pressure. If the pressure in the crankcase exceeds atmospheric pressure, the working fluid begins to squeeze out of the cavity of the unit through the leaks. This phenomenon is called “breather oil”. If the compression in the crankcase decreases, air mass with dust enters the crankcase cavity.

The princ ip of the breather plug’s operation

For an engine to work properly, it needs ventilation. In the area of the crankcase gases accumulate, the output of which must be provided. But the operation of this system can not be called ideal, because together with gases in the form of fine particles, the working fluid penetrates into the sump.

This problem is eliminated by installing a filter that traps the oil particles. The filter, however, does not solve the problem completely, because the working fluid gets into the breather in the form of vapors, which the filter cannot catch. This phenomenon is not very bad, however if the system is bleeding oil out through the breather, it is at least a reason to take measures to improve the engine’s technical condition.

The breather valve consists of the following components:

  • metal housing;
  • independent pressure spring;
  • rubber gasket (provides leak tightness at higher pressure);
  • locking nut;
  • device body.

Why is the oil flowing through the breather valve: causes

First of all, it is the wear and tear of the CPG. Usually, the rings are subject to wear, which causes an increase in pressure. As a result, the system begins to eject oil. Oil is escaping under high pressure, and the filters (usually a regular sieve) are not able to help.

Another common cause of the system throwing oil out through the breather is an oil slinger clogged to failure. If ventilation is broken, the working fluid, in the form of vapors, looks for workarounds around the wiper. Oil starts flying out through the breather.

The air filter can also become clogged. The system takes in air through other sources, which include the breather. Except that the air intake in this case is made together with the working fluid.

An increase in the level of the working fluid can also cause it to come out through the breather valve. Sometimes car owners don’t spare oil and pour it up to the very level, that goes against the manufacturer’s requirements. As a result, the excess fluid goes through the prompter.

Complete noise isolation of a car

The sump valve can jam, allowing gases to enter the crankcase. This leads to an increase in pressure in the system and, consequently, to the release of working fluid through the prompter.


If there is black or blue smoke coming from the exhaust, this is a sign of malfunctioning valves – they may have burned through. The rings could also be deformed. In this case, you need to measure the pressure in the cylinders. In gasoline engines it should be 11-13 MPa, in diesel – 20-32 MPa.

To understand the degree of contamination of the prompter, it is necessary to unscrew the spigots from the cover. If they are heavily contaminated, clean them with special agents or simply with gasoline. To check the oil separator you will have to unscrew several bolts. Then take out the unit and estimate its condition – if it is clogged with soot, wash and dry it.

Sometimes the valve can get a little wedged, which leads to penetration of gases into the crankcase and an increase in pressure. As a rule this problem is solved by flushing the unit. However, in order to flush it, you will have to dismantle it first.

In order to distinguish the piston ring lodging from the burn-out of one of the valves, we check the pressure in the cylinders – it is necessary to determine the cylinder with the lowest pressure. Then examine the spark plug of this cylinder. If the ringing occurred in this cylinder, there will be soot on the spark plug. If the problem is with the valve, the spark plug will look normal.

Solution to the problem

Starting to clean the breather, first of all look for the device under the hood and remove the air filter from it. Before doing this, the car is de-energized by disconnecting the minus terminal from the battery and turning off the ignition. There is an intake manifold under the filter – remove it too. After that you can see the prompter itself – as a rule its cover is fastened with two bolts, which should be unscrewed. After removing the cover you will see the oil baffle – it is fastened with a stud.

It is necessary to unscrew the nut located on the stud, but the stud itself shouldn’t be removed because it would be difficult to put it back on without dismantling the drip tray. We make a ramrod from a wire and use it to clean the tube. On the breather cap there is a flame-quenching brush – clean it too.

Changing the brake fluid on the Priora - choice of brake fluid

It remains to check the device. Start the engine, take off the plug from the oil filler neck, cover the neck with your palm. You can feel with your hand whether there is pressure. Then an assistant should press on the gas until reaching speeds of 100-130 km/h and once again check the compression by touching the palm. A small pressure already should be felt.

In order not to have problems with escape of working liquid through the prompter it is necessary to watch constantly its level. It is also important to pay attention to checking the filter and the transmission.

On the dipstick oil with bubbles: what is the cause? Small bubbles in the oil indicate a decrease in density and loss of its working properties. How to determine the cause of bubbles in oil and solve this problem, we will tell you in this article.

Emulsion on the dipstick oil level The appearance of emulsion on the oil dipstick is a serious cause for concern. There can be three main reasons for this. In this article, we will discuss these causes and how to solve this serious problem.

The turbine is pumping oil into the intercooler: what to do? Oil in the intercooler can cause serious malfunctions, up to the engine failure. In this article, we will tell you why oil appears in this node and how you can eliminate this problem.

Knocking of hydro-compensators: why does it occur and what to do? If hydrocompensators make an unpleasant noise, this is not yet a reason to panic. If you take urgent measures and do not delay a visit to the car service, the cost of eliminating the breakdown will be minimal.

Application of two-way valves in automobile systems Since in numerous automobile systems it is constantly necessary to close, redirect and mix various flows of liquids or gases, it is required to use various bypass devices, such as valves. Their operating principles are based on different actuators: pneumatic,

BMW E39 engine oil change instructions

Why is oil in the breather plug?

The symptoms of a clogged breather plug are greasing of the outer surface of the cylinder block in the area of the crankcase lead and oil dipstick, the air filter housing or the throttle valve. This problem is usually caused by untimely maintenance of the crankcase gas venting system or when the engine vigorously expels oil through the breather. The latter can be a sign of serious failures, including critical wear of parts of the cylinder-piston and valve groups.

Remove rust on the body of your car

The leak because of a trivial clogging of a branch pipe and an oil separator is also dangerous, as it leads to malfunction of the engine lubricating system. About all the main consequences and causes of oil escape from the breather and ways to prevent this phenomenon we will tell in this article.

Why oil escapes through the breather plug

Small amounts of oil in the breather is not a sign of malfunction . One of the functions of this node, is precisely the separation of suspended oil particles contained in the crankcase gases and return them to the engine. The main purpose of the breather is to relieve excess pressure in the piston space of the cylinder block by draining the mixture of water and fuel vapor into the intake manifold.

The breather plug in the crankcase ventilation system

To make it easier to understand why oil flows through the breather or dipstick, let’s briefly review the device and principle of operation of the crankcase gas ventilation system.

The design may vary slightly depending on the model, but always includes three main elements – the body, oil separator (oil reflector) and one or two pipes. On some vehicles, the breather is additionally fitted with a valve that opens when a certain pressure is reached in the crankcase or in the inlet vents.

The flexible hose can connect the crankcase outlet to the intake manifold, engine air cleaner housing and carburettor (directly, through the filter housing or valve cover) or the air vent in front of the throttle. The oil eliminator can be located in the breather housing, in a separate housing, as well as under the valve cover if the air outlet to the intake is arranged from under it.

Additionally the function of the oil catcher is performed by a flame arrestor built into the nozzle in the form of a spiral wire or mesh.

The general principle of all systems is the same: the crankcase gases enter the combustion chamber directly through the intake or carburetor and the oil they contain goes under the valve cover or into the crankcase.

Oil in the intake manifold through the breather

Oil trap clogged with sludge.

If the crankcase ventilation system is malfunctioning, the volume of crankcase gases or their oil content is too high, excess oil will escape through the breather, it will not be completely separated by the oil separator, and it will enter the intake manifold and carburetor with the gases.

Symptoms of crankcase ventilation system malfunction

    auto when the engine is running;
  • increased fuel and oil consumption;
  • traces of oil on the body and breather pipe outside or near them;
  • smoke from the oil filler neck when unscrewing the cap;
  • clogging of carburetor jets, greasing of air filter body, throttle body and intake manifold internals;
  • oil squeezing out through gaskets, seals, dipstick hole.
Connecting to the alarm system alarm car

Some car owners, faced with the problem of oil escape through the breather, disconnect its branch pipe from the intake or filter housing and turn it downward. This does not eliminate the root cause of the problem, but only prevents oil from entering the intake, carburetor and throttle. In addition, the toxic crankcase gases will partially end up in the interior of the car.

Causes of oil escaping through the breather, gaskets and seals

With a severely clogged breather, such high pressure is created in the under-piston space that oil from the crankcase can squeeze out even through the dipstick inspection hole, oil seals and engine gaskets. Therefore, at the first sign of malfunction you need to determine the causes of oil escape through the breather. The main problems and their consequences are listed in the table below.

Reason for the oil escape Why it happens Consequences
Critical piston ring wear, more rarely valve or piston burn-out Gases from the combustion chamber burst into the under-piston space. Venting system cannot cope with the increased volume. Compression drop, notable engine power reduction, difficulties with startup, thrashing, oil squeezing out through seals.
Wear of oil sealing caps. Excessive oil gets into combustion chamber, piston ring grooves get clogged. Due to poor fit of the valves to the seats, gases penetrate into the space above the valve, creating excessive pressure and disturbing crankcase ventilation system. Increased oil consumption, formation of soot on valve pads and seats, oiling of spark plugs, burnt-out valves, accelerated wear of piston rings.
Clogged oil slinger Clogging prevents oil particles in the crankcase gases from separating, causing them to enter the intake with the vapors. Clogging of the air filter, carburetor jets, throttle valve, deterioration of engine operation due to violation of the composition of the fuel-air mixture.
Clogged breather pipe. Oil is released together with crankcase gases as a result of pressure increase in the crankcase due to inability to bleed it through the breather. Oil squeezed out through the dipstick hole, sump gasket, crankshaft oil seal and other seals. Possible disconnection of the pipe from the breather outlet or penetration of gases through the cracks formed in it.
Dead breather valve Sticking valve does not release pressure when pressure rises above allowable limits. Oil squeezed out through the seals due to inoperative venting system, TNT, deterioration of engine operation due to excessive pressure in the piston space.
Clogged air filter Due to the reduced capacity of the filter, oil particles from the crankcase ventilation system are sucking in. Clogged carburettor jets, throttle valve (on injector models), violation of air-fuel mixture composition.
Oil level exceeded. Excessive oil together with gases gets into the breather valve, oil separator can not cope with their drainage. Rapid clogging of oil separator, buildup of oil in the hose, its ingress into the inlet manifold.
Installation of rear view camera and monitor

Diagnostics and elimination of causes

If you have a problem where the engine is throwing oil out through the breather, inspect the intake system, crankcase ventilation and do engine diagnostics. Start with the air filter and its housing to correct the issue and cause. Replace a clogged filter element, and use a cleaner to remove the grease on the components.

Diagnosing why the oil squirted out through the breather plug: video

  1. Check the oil level in the engine by turning it off and waiting at least 15 minutes. The level must not exceed the maximum mark on the dipstick by more than 5 mm. Excess oil should be pumped out through the dipstick hole.
  2. Inspect the crankcase ventilation system for cracks or clogs in the connector, oil clots in the oil separator, and check the PVC valve (if any) for proper operation. Remove contaminants by flushing with solvent, gasoline, diesel fuel or kerosene. Failed elements are to be replaced.
  3. Diagnose the condition of the engine. First of all unscrew the plugs and examine them. The presence of black glossy coating definitely indicates an excess of oil in the combustion chamber. Consistently we measure compression in cylinders.

Normal value for the diesel 24-30 atm, for injector cars 12-14 atm, for the carburetor not less than 10 atm. The exact value for your model can be calculated by multiplying the compression ratio of the engine by 1.4.

The difference between the cylinders should not exceed 1 bar. Decreased compression indicates a leaky combustion chamber due to a burned-out valve, piston, wear or piston rings. If the compression is normal, but there are traces of oiling in the chamber, it is necessary to check the oil caps.

How do I clean the breather plug?

To clean the breather, you need to disconnect the branch pipe, remove from the engine and disassemble the housing, remove the oil separator and valve (if available). Wash all parts with gasoline, kerosene or diesel fuel, removing oil deposits. Dry and reassemble in reverse order.

( No ratings yet )
Like this post? Please share to your friends:
Leave a Reply

;-) :| :x :twisted: :smile: :shock: :sad: :roll: :razz: :oops: :o :mrgreen: :lol: :idea: :grin: :evil: :cry: :cool: :arrow: :???: :?: :!: