PCV valve education

Posted By: kilroy

PCV valve education - 02/25/12 04:24 PM

Ok I know the gist of the PCV valve operation (or I thought I did)
couple of questions...

With all the talk of PCV on 4.7 engines and with my Durango and using some oil mysteriously lately (which is not showing up on the plugs) I thought it was time to clear the water on a few questions.

1. Should a PCV valve have full vacuum present on the motor side of the valve at IDLE, or should it be sucked closed?

2. What are the symptoms of a stuck open PCV?

3. Does anyone know if the PCV on a 02 Durango is spring loaded or is it just a "rattle" valve?

Posted By: kilroy

Re: PCV valve education - 02/26/12 03:38 AM

how about just 1 or 2.

Posted By: Dcuda69

Re: PCV valve education - 02/26/12 04:16 AM

Does this help??

Attached picture 7090451-PCVflow.PNG

Posted By: Dcuda69

Re: PCV valve education - 02/26/12 04:20 AM

Another??

Posted By: kilroy

Re: PCV valve education - 02/26/12 04:26 AM

Ive got full vacuum at idle in my durango. When I put my finger over it I can hear the valve snap inside, but It has FULL vacuum at idle and I couldn't get a straight answer googling things. Would this cause some oil consumption.

Posted By: Dcuda69

Re: PCV valve education - 02/26/12 04:35 AM

Quote:

Ive got full vacuum at idle in my durango. When I put my finger over it I can hear the valve snap inside, but It has FULL vacuum at idle and I couldn't get a straight answer googling things. Would this cause some oil consumption.

That sounds pretty normal....if in doubt just replace the valve(with the correct, quality part)Don't forget to check the fresh air side of the pcv system.

Posted By: Cab_Burge

Re: PCV valve education - 02/26/12 05:38 AM

The PCV has a spring and check valve inside it, the spring keeps the valve closed when the motor IS NOT running, some PVC will close at WOT, some don't depending on if the motor has vacume at WOT

It sounds like yours is operating correctly, vacume is high on stock motors at idle, you put your finger over the PVC end and the spring inside did its job, it closed the valve

Their designed to suck the bad fumes out of the crankcase when the motor is running, they do a outstanding job of sucking any water or condensation out of the motor also

Posted By: kilroy

Re: PCV valve education - 02/26/12 02:24 PM

Quote:

... It sounds like yours is operating correctly, vacume is high on stock motors at idle, you put your finger over the PVC end and the spring inside did its job, it closed the valve ....

Thing is if its suppose to close the valve then I should have no vacuum after I put my finger over the end of the PCV. But its still trying to suck my finger through and the valve is not "fluttering". Im going to replace it, but Im just trying to get an understanding of what it should do and what happens when its stuck open, I know what happens when its stuck close.

Posted By: 360view

Re: PCV valve education - 02/26/12 07:28 PM

It was interesting that on the cast iron 8l v10 Chrysler went with a fixed orifice instead of a rattle type PCV

Here s another variation

http://www.envalve.com/why.html

In theory
Having a low vacuum inside the block
During part throttle cruise
Would give a slight fuel economy benefit
... The backside of the piston would not be fighting against a pressure and internal moving parts would encounter "wind age" aerodynamic losses

Posted By: fox

Re: PCV valve education - 02/27/12 01:59 PM

Quote:

Ive got full vacuum at idle in my durango. When I put my finger over it I can hear the valve snap inside, but It has FULL vacuum at idle and I couldn't get a straight answer googling things. Would this cause some oil consumption.

A stuck or imoperative PCV valve can cause a motor to gum up and then use oil.
But, I've never seen one working cause it.
The PCV valve really never completely closes, tha tI've seen. They open fully at low vacuum/WOT.