I had a replacement pcv valve replaced a couple of years ago and wonder if there is an easy check to ensure it is doing what it should? I have been considering pulling off the pipe which connects to the back of the valve and blocking the pipe with my finger to feel either a suction or a blow. Don't know which it should be. The engine will be idling so perhaps not much pressure or suction.

In that case you have to take it totally off both from the pipe and the engine and then put it in your mouth and blow or / suck air from her two edges. From one side you can blow and from the other you cannot. It is one way valve with a diaphragm in her. 

 

But i suggest you not to do so as it will probably brake apart as it is made from hard plastic that gets brittle by the time and then you will need a new one. 

 

They most often brake from pipe's side and keep in mind that at engine's side there is a tiny o-ring that does not come with the new pcv valve. 

 

As the pcv controls the air pressure within the engine, if your valve was erratic you would find moisture in oil's cap. 

Edited 30 August, 20223 yr by stratosg