Everything You Should Know About Oil Breathers

Like the human body, the blood circulating in the body must be healthy to function correctly. The same is true for machines; lubricant health should be in good condition to acquire higher machine reliability.

Oil breathers are essential in ensuring the oil is kept in optimal condition. Besides this, oil breathers stop the air pressure buildup within an enclosed system containing oil. Because of pressure buildup and not efficiently vented, you will face oil contamination, oil leaks, and loss of power. Let’s know what is oil breathers in detail below:

Oil Breathers

What Are Oil Breathers?

All modern cars need some oil breather system. In a petrol engine, some combustion gasses inevitably ‘leak’ past the piston rings and into the crankcase. The turbocharged engines suffer more badly because the cylinder gasses are under more pressure.

This activity of gasses coming into the crankcase makes crankcase pressure, which needs to be vented. And that’s where an oil breather system comes in.

What Does An Oil Breather Do?

An oil breather system allows the pressure to escape. If this pressure isn’t efficiently dissipated, oil can leak from crank seals, gaskets, and dipstick tubes. The reason is that oil comes out effectively due to increasing crankcase pressure.  The oil breathing system allows this pressure to build up. Usually, they will include a separator box that will catch oil suspended in the gasses. Then, allow it to drain back into the sump.

The gasses are then vented to reduce the pressure. On older cars, this meant venting the breather pipe to the atmosphere. But the breather pipe returns to the engine inlet on all modern cars. This helps decrease emissions and prevents the vehicle from releasing oily residue directly onto the road. That means the engine is fed an oily mixture from the crankcase instead of ingesting fresh, clean air. It can cause problems with the inlet pipe, throttle body, and other parts of the inlet tract.

Oil Breathers Functions And Types:

There are four types of oil breathers. There are engine oil breathers, hydraulic oil breathers, transmission oil breathers, and Axle oil breathers. All of these breathers have different functions. Let’s know their functions individually below:

Engine Oil Breathers or Crankcase Breathers:

During combustion, some combustion gasses pass the piston rings and enter the crankcase. The breather is located inside the engine and bends downwards. Hence, this breather helps pressurize the crankcase by releasing gasses into the environment. This helps achieve adequate machine performance, inadequate oil consumption, and less oil loss.

Hydraulic Oil Breathers:

These breathers are mounted on hydraulic tanks to prevent water and pollutants from entering the system. They help to eliminate pressure or vacuum buildup because of temperature or volume changes.

Transmission Oil Breathers:

To balance air pressure on the transmission, these breathers are mounted. The inside air expands during car operation due to transmission oil heat and cooling. Built-in filtration media prevents the ingress of pollutants and moisture, which can enter the system with air suction.

Axle Oil Breathers:

Axle oil breathers are mounted on the differential housing. During operation, the inside air of the axle assembly heats and extends, enhancing the pressure. You need to extract the pressure from the atmosphere. When the axle assembly cools, the air inside is compressed, creating a vacuum. Breathing helps to serve this process.

How to Replace Oil Breathers

For oil breather replacement, you should do the following:

First, you need an oil breather to replace your old oil breather.

  • Lift and pull four tabs up
  • The top cover will come off

Step 1.

The bottom should come out and be held in place with the three clip tabs. You may need a flat-head screwdriver to push and pull the tab down.

Step 2.

Now remove the pollen filter housing; it is held with six bolts. If you want to replace the pollen filter, remove this assembly.

Step 3.

Remove the two covers on each side of the vehicle. One covers the brake fluid reservoir, and the other covers the electrical cabinet. They are clipped on by two tabs and one rubber tab you slide off.

Step 4.

Turn the sensor clockwise, release the two clips, and remove it.

Step 5.

Undo the plug for the bonnet pin on the other side and move the path.

Step 6.

Pull the washer fluid pipe out of the clip and out of the way.

Step 7.

You have two bolts to remove on either side. Pull the entire scuttle panel towards you, and it will come out. You must remove the engine cover and hold it in place with the five bolts. Lift the cover-up towards you. Remove the filler cap; otherwise, the cover won’t come off. It prevents accidental falls; put the oil breather cap back on.

Step 8.

The oil breather is located in the upper left corner, facing the engine bay. The side pipe is held in place with three bolts and one bolt.

Step 9.

Undo the bolts and lift them. After that, twist off the side pipe with a green washer. Actually, new oil breathers and old oil breathers are not much different.

Step 10.

But if you inspect closely, you can find that the old rubber diaphragm is weaker than the new one. However, you are done.

Oil Breather Pipe Symptoms:

Bad oil breather pipes can cause a variety of problems for your vehicle. That’s why you should recognize the symptoms and address them early. Have a look:

Oil Discharge

In most cases, oil leakage is the first clogged filter symptom. The filter’s primary role is to prevent debris and other pollutants from entering the engine. Because of blocked breather filters, pressure will build up. And this high pressure can cause gaskets and seals to blow. As a result, your car’s engine will begin to leak oil, or you may notice sludge in your intake manifold.

High Idle

A lousy oil breather can impact your vehicle’s idling speed. When the filter is clogged, it can cause a high idle speed. This aspect is due to oil blockage or leakage in the engine. Therefore, a change in idle speed indicates problems if your car has a crankcase breather filter.

Engine Poor Performance

Another symptom of a blocked CCV filter is reduced engine performance in your vehicle. Clogged filters affect air-fuel flow, which affects vehicle acceleration and power. You may especially face this problem if you drive at low speeds.

Nevertheless, several other factors affect the performance of the engine. This is why it is essential to consult your dealership, a professional mechanic.

Check the Engine Light On

As with other engine-related problems, an illuminated check engine light is a symptom you should notice. Though this cause isn’t related to the CCV filter, it results from your engine’s ECM or PCM.

Purpose Of Oil Breather On Motorcycle:

A breather or vent pipe allows an internal explosion motor to vent crankcase pressure from the engine. It is actually called a crankcase ventilation pipe. The piston rings are allowed to seal tightly against the cylinder walls by extracting pressure from the crankcase. Moreover, it offers excellent compression and lower oil consumption while producing more horsepower. You can find this pipe on a valve cover. In fact, It is also recognized as the oil drain location in the engine.

How Does An Oil Breather Can Work?

The oil breather can supplement the breather hose between the engine’s intake system and PCV. The breather hose is disconnected from the air intake and replaced directly with the can input. Air travels through a tube from the catch can bottom to the outlet through a filter.

A hose completes the circuit and reconnects to the air intake port. When air passes through the catch can, it traps the oil particles. Before falling down the can, it aggregates them into larger droplets. Cans are fitted with a drain plug to eliminate oil catchment periodically. Under normal conditions, you don’t need to maintain these cans between regular service intervals.

Final Word

On the other hand, you should check the Oil breather conditions at each scheduled maintenance interval. Hence, you must replace the breathers if their condition is severe. To know the breather works in good condition, you must pass compressed air through the breathers.

Usually, if breathing is not stopped, air will pass through the respiratory system. Ultimately, you can only use this method to test the transmission and axle breathers. For hydraulic breathing, visual inspection is usually done to check the condition. At last, we have given the proper information about the oil breathers. After reading this blog post, we hope you can solve any breathing problem.


I am Engr. Z Eusuf Lubricant Specialist, Mechanical Engineer & has been working with engine lubricants for a long time and knows what makes them work best. I can help you find the right oil for your needs, and I have tips on how to keep your engine running at its best.