Is the PCV valve a one way valve?

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Apr 27, 2010
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I'm checking the valve in my Explorer while the manifold is off to change the plugs and the valve is easier to get to. I have it out and it rattles fine when I shake it. I can suck on the vacuum hose end of it without effort. I can also blow into it with only little resistance. Isn't it a one way valve so I shouldn't be able to blow into it at all? Be that as it may, does that even matter, as I can't see a time when that would be important as there is always some vacuum on it. It's not a turbo engine.

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It is one-way when vacuum applied, but not when positive pressure is applied.

Hell IDK, I’d just replace the danged thing and be done with it. Bigger fish are likely waiting to be fried.
 
Blowing into one end you should feel resistance. If there is no or little resistance the valve doesn't seal well, maybe due to crud.
 
Yes some resistance when I blow through it but I can still blow through. Thought that shouldn't be the case, so it seems it's ok then.
Sucking on it is testing it how it normally operates. Blowing into it isn’t a good test since the engine is n/a and not forced induction.

The fact that it passes the vacuum test is good. Whether or not it has passed the boost test isn’t really important since it won’t be subjected to that condition on your engine, right?

Nevertheless, I would consider replacing it as a preventative maintenance task…if a new one is not prohibitively expensive, that is (and is locally available).
 
They were one way back in carburetor days for backfire protection. How long since your car had a backfire through the intake ? That's why they are just metered holes these days.
 
The ones that do have a moving part are designed to provide a more constant flow. As the pressure across the valve increases (high manifold vacuum), the plunger moves to close down the orifice and prevent the flow from increasing dramatically. It may or may not act as a one way valve. The valve's operation with reverse pressure is undefined since that doesn't happen on the engine.
 
Turbo or supercharged cars with the pressurized intakes will have actual check valve PCVs that stop all flow towards the crankcase.
 
Manifold vacuum holds the PCV closed but only partially. Air will still get through. This is done so when vacuum is high, the way the engine normally runs, at least some air will be pulled from the engine internals. When you mash the throttle and vacuum drops to near zero the PCV will be wide open.

Shaking the PCV and hearing it rattle only tells you the valve is free and not plugged. It won't tell you if it's working properly. If I went through the trouble of removing the intake I would replace it.
 
What year Explorer and with which engine?
I ask because my '05 Ranger (4.0l SOHC) has an identical looking PCV valve.

1) Mine has the aluminum heating pipe which sets into the ring where the "PA66-etc." can be seen. Some people eliminate this feature claiming it's ineffective.
2) I've read to change 'em every 4th oil change in warm climates and every 3rd in cold. Mine was original and 15 years old so I didn't need to check the weather.
3) Mine rattled but sounded like it was gunked up a bit.
4) One fellow urged using an OE replacement citing matched performance in a given engine. I read this after installing an AZ part.
5) I figure cleaning them is wasteful as the spring must age.
 
Like I stated in the other PCV post, just change it.. My 02 Ford Taurus PVC valve shook fine, and I cleaned it out with brake fluid.. A decent amount of crud came out and I reinstalled it and there was zero effect on the engine operation.

Ordered some vacuum hoses from Rock Auto, and the valve was under $5 I think. I just bought it and when I changed the valve, the engine performed drastically better! More power, idle smoothed out significantly, very big effect on the operation of the engine. That was before I changed any other part of the engine, only part changed at that point was the valve.
 
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Rock Auto has the Motorcraft PCV Valve for $4.84..

https://www.rockauto.com/en/catalog...sitive+crankcase+ventilation+(pcv)+valve,5052

I forgot to mention that I used the MC valve.. As a matter of fact, I only use Motorcraft parts on my Ford engine management systems. Vacuum hoses and connectors when the cost isn't prohibitive or there is no availability issues. Sensors or other electrical parts when there is not a newer design to "fix" a factory issue, and most other parts when there is an actual quality issue with aftermarket parts.

Do you belong to a Ford Explorer forum?

https://www.fordexplorer.org/

https://www.fordforum.com/forum/ford-explorer-20/

https://www.explorertalk.com/
This one seems to be a better site with more posts. I belong to a super low population Taurus forum where a few guys have done almost anything you can think of to these cars. I'm lucky to have it, even if its a low post forum. Figured out a few gremlins there, very helpful and has kept my greys in check fixing my darn 20 year old car.
 
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