i have another post that ended up leading me to check my pcv valve, and i think it might be bad. the guy at autozone told me that if you blow in it you should only be able to feel the air through one end, not both ways. if it does that then its no good. is this true? last time i changed it the guy told me to shake it, and if it didn't move freely then it was no good...that's what was wrong with my last one, but i just changed it not long ago.

 

You can blow through it in either direction. It's a spring-loaded calibrated vacuum leak, basically. Engine vacuum pulls the piston inside up against the force of a spring, closing off the valve except for a small, calibrated, orifice that draws a small amount of air through the engine, evacuating blow-by gasses, oil vapors, etc. from the engine and burning them along with the rest of the A/F mix. When vacuum drops near zero (WOT) the spring opens the valve fully allowing a larger amount of airflow to clear out the greater amount of blow-by that happens at heavy/wide open throttle.

But they aren't one-way valves. They'll flow in either direction if you're just bench testing them. Only engine vacuum assures the vapors flow one way when installed on the engine.

 

yeah that's what i thought too...i just bought a new one anyways since they're like 3 bucks and new parts is always good..and it blew through both sides also, so yeah i kinda figured he was wrong or maybe i misunderstood what he was saying.but how WOULD you tell if it was bad then? just like the first guy told me? by shaking it?

 

Well they're cheap enough that if I ever had any reason at all to suspect one was bad, I'd just relace it.

 

The easiest way I've found to check it was to shake it. If it rattles, more than likely it's good. If it doesn't rattle it's clogged and isn't good.

 

Should oil be able to flow back into the intake? my pcv valve shakes freely, blows both directions, but when we took it out, it was coated in oil. a large amount of oil came out of where the hose connects to the intake.

 

That's blowby - all engines have it, some worse than others. It's oil that blows by the rings. That's the whole purpose of the PCV, to collect that oil and gases and burn them up.

 

Thanks. My friend and i have torn apart the plenum and throttle body to inspect and stuff. on the passenger side valve cover, where the pcv valve should go, someone rigged up a plastic elbow with nothing to stop oil just blowing through into the intake. i'm assuming that would be just to put in another new pcv valve?

 

The PCV and this elbow replace the old breather caps. They take the fumes and some of the blowby and pull it back into the intake to be re-burned, it's part of the emissions system.
My car has a PCV valve on the drivers side valve cover. On the passenger side I have an elbow that goes up to the air cleaner with nothing but a little white filter on the inside of the air cleaner assembly (in addition to the normal air filter).