Most vehicles on the road today have a Positive Crankcase Ventilation (PCV) or a form of it. In the next three articles we will discuss how PCV works while a vehicle engine is operating, what the purpose of it is, and what the symptoms and consequences of a failing PCV system are.
Let's start with the basics of an internal combustion engine operation. There's a series of cylinders that a piston moves up and down inside. A mixture of air and gas is pumped through the passages of the intake manifold into the intake valve of each cylinder. Spark is transferred from the spark plugs causing the mixture of air and fuel to explode in the open space at the top of the cylinder that is called the combustion chamber. The pressure from the explosion causes the piston to move down, which causes the crankshaft to rotate and push the piston back up. The motion pushes leftover air and fuel out of the cylinder through the exhaust valve. The movement is the engine operating and then it transfers power to the transmission for vehicle movement. There is air and fuel mixture pulled down by the piston and piston rings into the crankcase, which insulates the escaping fuel mixture that is called blow-by, an unavoidable byproduct of the operation of the engine. It can cause a buildup in the engine and problems in the crankcase.
Blow-by used to be vented into our environment. In the early '60s, vehicle manufacturers developed the PCV system with a valve intended to help and was one of the early devices of emission control. The PCV system was designed to recycle the blow-by gases by pumping them back through the intake manifold passages, valves and cylinders for another attempt of complete usage of the air and fuel mixture during the internal combustion action.
Next time we will talk about the purpose and operation of the PCV system.