Would a Bad PCV Valve Cause Valve Cover Leaks?

[ilko]

I just changed my valve cover gaskets over the weekend. When I took the covers off and looked at the hoses leading to the PCV Valve I saw a small amount of crud.

That got me thinking. Could a plugged up PCV valve be the cause of my valve covers developing leaks... Pressure builds up inside the valve housings and if it can't be relieved through the PCV system, then the only other way is through the VC gaskets. Does this make sense?

[dparm]

Yes, a failed valve can cause leaks. Remove yours, shake it and listen. Should be pretty obvious if it's bad or not.



Here's some good diagrams:

http://www.agcoauto.com/content/plug..._articleid=197

[Lefthook]

Yes, a failed valve can cause leaks. Remove yours, shake it and listen. Should be pretty obvious if it's bad or not.



Here's some good diagrams:

http://www.agcoauto.com/content/plug..._articleid=197

I thought our PCV's had a diaphragm and were immune to the shake test?

[noznab]

Shake test doesn't always work. I replaced mine ~60k miles and there was nothing visibly/audibly wrong with it. Noticed a significant difference in oil consumption with the new one too.

[Apat]

When in doubt.......replace it.

[dparm]

I thought our PCV's had a diaphragm and were immune to the shake test?

True, if it's in early stages of failure you may not know.

[PitchS4]

I agree, mine passed the shake test but did this...

https://www.youtube.com/watch?v=rf_B...e_gdata_player

All good with the new one.

[ilko]

ROFLMAO, love the honk!

Any pointers on how to take out the PCV valve? The lower connector seems incredibly hard to get to...

Thanks!

[PitchS4]

It is really easy logistically, just a huge PITA because of the tight space. Take a look ahead of time and make sure you get the correct new clamps. The OEM one has one-time-use clamps you will need to destroy.

[ilko]

Thanks. Trust me I have a shitload of clamps from my 1.8T days

[ilko]

So I replaced the PCV valve with a $55 Vaico unit that I bought from partstrain.com (use code PTCART for 10% off and free shipping, as very helpfully posted by Amsterdamned in another thread).

To make the install much much easier you need to remove the PCV pipe from the driver side valve cover. Other than that it's a piece of cake. Now that I've done it once it's a 15-20 min job.

What I noticed afterwards is that my fuel economy increased by 2 MPG overall. Does that even make sense? On Saturday I drove for 60 miles around some mountain roads and got 23.5 MPG and that was with some heavy acceleration at times. Last night I drove for 110 miles on the highway and got 25.5 MPG. I was doing 80 MPH for a good portion of that trip.

Both of these trips I've done multiple times in my B6 1.8T and generally have only gotten 2-3 MPG better in that car. If indeed true, that's very impressive.

[JimmyBones]

Automatic?

[ilko]

Yep.

[04 S4]

Where is it located on our motors?

[dparm]

If you pop off the four-rings plastic engine cover, it's the black disc shaped thing mounted on the backside of the engine (by the firewall).

[ilko]

Here it is:

[SlideWays]

For people who replaced PCV:

How much were you consuming before? And how much has that changed after replacement?

[ilko]

Well mine hasn't used any oil in the last 2000 miles since I bought it. But I changed the PCV valve because I noticed a few small deposits on the PCV lines at the top of the valve covers when replacing the VC gaskets so I figured might as well do that too.

[04 S4]

aweseom, thanks! that looks like a PITA to get to lol. Gotta be done though lol.

[B6JoeS4]

The shake test does not work on our PCV. It's a rubber diaphram and a spring. Nothing to shake here.

[lqmeh]

The shake test does not work on our PCV. It's a rubber diaphram and a spring. Nothing to shake here.

Lol joe.... big and bold enough eh?

Did you RTV your VC gaskets when you put them back in? If not, they'll likely be leaking again in a few thousand miles or so.

[04 S4]

I didnt RTV the gaskets themselves, just the half moons...