What is a pcv valve?

Pcv valve

I don't think a car has been built in the last 40 years that doesn't have a PCV valve. My 1965 Galaxie had one, but my 64 Ford pickup didn't. PCV means "Positive Crankcase Ventilation", in other words actively sucking junk out of the crankcase rather than just letting it be vented to the air.

The PCV valve allows unburned stuff that blows by the piston to be collected and re-burned rather than just vented to the air, without causing your engine to stall out at idle. This results in a serious reduction in air pollution at virtually no cost, which is why it was the first emissions control device employed.

Look on top of the valve cover. There should be a knob sticking out with a small diameter rubber hose attached to it. It will be inserted in a rubber grommet. You can just pull it out of the valve cover. If it's clogged it will be unnecessarily blowing junk into the air; if it's leaking, it will seriously foul up operation of your engine, especially at idle. They cost about two bucks and you can change it with your bare hands. Replace often. The book says 24000 miles/24 months. I always write the replacement date on them with a Sharpie so I can remember when I replaced it last.

First answer by Ganderton. Last edit by Ganderton. Contributor trust: 1819 [recommend contributor]. Question popularity: 21 [recommend question]