Testing PCV valve
 

Hi all

just needed some help with the old girl.What i'm getting on the 1st start up is the revs fluttering up and down for about 10 secs before it settles down. I have cleaned the TB and also the PCV Valve which was changed at the start of the year.
I have also given the MAF a clean too. The car seems to run fine once on the moving .Is there a easy way to test the PCV Valve, I have blocked the top pipe on the unit and sucked/blowed on the lower one and i can hear the diaphragm open and close. Is this normal as what it mean to do.

many thanks all for the help +++

Check out quattroworld, lots of PCV posts there. Its really very simply made, just a orange rubber diaphragm in a two-piece plastic casing, and a return spring. Its easy to dismantle.
I can only think of two reasons why it wouldnt work:
1. its so clogged up with caked oil the diaphragm cant move properly
2. the diaphragm is punctured or disintegrated

http://forums.quattroworld.com/a8/msgs/80088.phtml

http://forums.quattroworld.com/a8/msgs/79849.phtml

Here is a post with a picture:

http://forums.quattroworld.com/a8/msgs/70936.phtml

Warning, old thread revival!

Interesting...
I've been having PCV issues since replacing mine earlier this year.
Oil smell I had seems to have gone, and the car seems to run well, but I've got an awful groan/honk noise.

Gorans links to QW proved to be something I had read before, but made for a good refresher.
I wish I had cleaned the old one just at the moment! And if course now I can't find it!
Might pinch the Silver '02s valve or try the WD40 down the nozzle trick...

Does anyone know why the cheaper/aftermarket PCVs are so troublesome on the 40V engines?



Also I've checked Bentley, the tech dump, online ETKA (realoem.com) and Jim Ellis parts and nothing seems to have much of a breakdown of the operation of the PCV system.
There's no trouble shooting or explanations and incomplete exploded diagrams. It also looks as though the breather system gets confused with the upper engine oil retention system, as that's where the incomplete diagram is found...

I recall taking the PCV out and cleaning it ages ago, can't even recall if it was this or the previous S8....
BUT it's dead easy to do and easy to get at.

IIRC once I'd taken mine apart and cleaned it up I found a tear on the edge of the orange diaphragm. After cleaning and reassembly it seemed to work OK (tested by sucking and blowing on the various orifices!) but I replaced it anyway.

Thanks Andrew,

I'm actually on my third valve and scratching my head!
The second valve was a Meyle (should be quality replacement), so I might open that one up and take a look while its sitting on the bench...

Did you replace with OEM?

I think so.
Even kept the old one as an emergency spare as the damage was so close to the edge seal that I reckoned it was probably going to be OK for temporary use, with a bit of suitable adhesive on the tear.

This is the best picture of the system I've found.

I'll take a look on the car shortly to see where the hose #10 attaches. I'm thinking it might attach to the venturi suction pump that goes into the intake elbow, but I'm not sure yet

https://www.realoem.me/img/Bilder/255/255103970.png

Just an update on this:
I sprayed some WD40 down the venting nozzles if the newer PCV on the car.
Initially it quieted down a little, but still had a regular (muted) 'honk'. Over the next couple of days it all disappeared though, so for now I'm happy +++



Note: on the diagram I posted above, number 10 hose plugs into the top of the valve cover at the rear of the left hand head. PCV function mystery continues....