I replace my PCV valve once a year whether it needs it or not. The last changeout was around 6 months ago. Today I pulled the PCV valve out of the hole that it plugs into in the valve cover and the engine did not rev up like usual when the PCV valve is pulled out. I put my finger over the hole on the bottom of the PCV valve and it was sucking air into the PCV valve. However, when I pulled the PCV valve off of the rubber angle-shaped boot that connects it to the hose that goes to the engine, the engine revved up very much. I then wiped the PCV valve off, placed it into my mouth, and blew into both ends. I was able to blow air through the PCV valve in both directions, but I always thought that the PCV valve would not pass air both directions. Am I correct about this? I shook the valve back and forth and I could hear the plunger inside the PCV valve going back and forth as I was shaking it. Although this is a fairly new valve, is it likely that it is bad? This is on a 94 Corsica with a 6 cylinder engine.
PCV valve question
Jan 29, 2007
3 Replies
That should be normal operation. You don't want the valve pulling full vacuum. The shake test is one way of telling the condition of the valve. A rattle is good.
The valve is designed to pass a small amount of air at idle; the manifold vacuum will pull it mostly shut, and the valve will open as the throttle opens and vacuum falls off. It should slam shut if there's a backfire in the manifold; that's its purpose, to keep flame from reaching the flammable gases in the crankcase. If it didn't bang shut you might have to pick up a lot of pieces off the road.
Dan
The valve should last at least 60,000 miles, it doesn't need yearly replacement. I'm still running the original on my 127,000 mile 92 explorer.
Join the Discussion
Have something to add? Share your thoughts — no account required.
Didn't find your answer?
Ask the community — no account required