Whenever the spark plug of a vehicle fires, the pollution of the crankcase oil elevates, creating harmful byproducts. Some of these gases get forced around the piston ring and go down through the crankcase. 

The oil vapours present in the crankcase mix up with these gases, creating harmful substances that could damage your vehicle’s engine. This is where the positive crankcase ventilation comes into play. 

This system filters out harmful gases into the crankcase. Read on to know more in the following sections that mention the working of this system in detail. 

Positive crankcase ventilation helps filter harmful gases into the crankcase, ensuring that the vehicle’s engine remains unharmed. 

The valves in this system use the engine’s vacuum to pull out air from the crankcase and reintroduce it to the manifold system. This process provides another chance to the uncombusted nitrous oxide hydrocarbons another chance to complete combustion.

To understand how the positive crankcase ventilation works, you need to know a bit about the combustion engine as well first.

• Hollow cylinders surround an internal combustion engine. Each of these cylinders contains a piston that glides up and down. Now, a mixture of gasoline and air is pumped through several tubes, called the intake manifold, through the cylinder's intake valve. 
• While this happens, a spark from the spark plug pushes the mixture into the combustion chamber, which is an open space at the top of the cylinder. 
• The pressure created due to this explosion further pushes the piston in the cylinder, causing rotation in the crankshaft. 
• The crankshaft gears in tandem with the car’s transmission system, making the car move. The piston pushes the leftover gas and air from the cylinder to the exhaust valve. 
• However, some amount of gas gets pulled down by the piston, which shifts to the crankcase. This is an unavoidable circumstance which can cause issues with the engine. 
• Positive crankcase ventilation is a process which involves filtering of these gases through a valve to the intake manifold. From there, these harmful gases are transferred to the cylinders for another round of combustion. 

• The crankcase, which is found underneath the crankshaft, acts as a space for storing oil in automobiles. It prohibits direct contact between the crankshaft and oil to avoid harm to the engine. 
• However, blow-by gases and oil vapours can interact. An oil and air separator is used to stop this, even though it's not desirable for these vapours to reenter the cylinders with the gases due to their higher combustibility. 
• Oil vapours could lead to problems, including poor performance and mishaps. The separator also stops oily debris from coating the air intake, which could eventually block airflow. 
• The primary idea behind an oil and air separator is to remove any oil from the air before it goes back to the intake manifold and place it either back in the crankcase or in a little container known as a catch can. 

Evidently, positive crankcase ventilation is a useful system which ensures the smooth functioning of a vehicle’s engine. By filtering out harmful substances and sending them back to the exhaust manifold, this process ensures that you enjoy a safe and comfortable ride.