PCV fun! 3 way check valve goes where? enlarging pcv hoses/valves?

[traffico]

I know there are several slightly varying pcv systems across the 1.8 motors... Mine has two metal nipples off the valve cover. My first question is what do i do with the 3 way check valve that is in the line off the smaller valve cover nipple? I know where the larger 2 ports of this valve go and understand it is to allow the valve cover to vent into the manifold when throttle plate is closed, but I can't for the life of me find out where the third and smaller port on this 3 way goes to. Vacuum source? SAI?

Also I have a disconnected nipple at the back of my n112 valve, there are two ports of the n112 right? One goes to combination valve and the other? to the charcoal canister? my exhaust is all custom has my canister probably been deleted?

Lastly... Due to running high(ish) boost and my motor being worn out, I want to allow for good breathing of what is realistically probably 'excessive' blow by. Any thoughts on enlarging my pcv ducts and valves? just make sure the valves have similar differentials/specs for operation??

Thanks!

[traffico]

3Way check valve? Anyone?

[old guy]

3Way check valve? Anyone?

The N112 should have one port blocked off. What year is your A4? There are several different block breather arrangements depending upon the manufacturing date.

[userbob0001]

I know there are several slightly varying pcv systems across the 1.8 motors... Mine has two metal nipples off the valve cover. My first question is what do i do with the 3 way check valve that is in the line off the smaller valve cover nipple? I know where the larger 2 ports of this valve go and understand it is to allow the valve cover to vent into the manifold when throttle plate is closed, but I can't for the life of me find out where the third and smaller port on this 3 way goes to. Vacuum source? SAI?

I think we'll need some clarification here, but if you're talking about the three way valve that comes off of the block that acts as the PCV valve, check the nipple that is attached to the port at the back of the head.

Also I have a disconnected nipple at the back of my n112 valve, there are two ports of the n112 right? One goes to combination valve and the other? to the charcoal canister? my exhaust is all custom has my canister probably been deleted?

It goes to the vacuum canister. I would expect you to still have both, but there's no telling over the internet.

[traffico]

thanks... It's this one http://www.googleadservices.com/page...%3D17242791492 it's right off the smaller of the two ports on my valve cover and a tee into the line that goes to the intake manifold from the main larger ccv valve... The larger ports on this 3way go to the above locations, the 3rd port is tiny and the closest diagrams I can find suggest it may go to another check valve and then to manifold. Mine is a 2003 b6 vin pre-500...

[traffico]

When I was pulling the system apart, this valve had the small port plugged and did not flow in either of the two other directions, pos why I had a lot of valve cover pressure at idle... I can replace it with a two way which is what I was about to do... Is it possibly a vacuum actuated valve? so manifold vacuum opens it via the third port, and is checked upstream so this actuator port doesn't get boost

[old guy]

When I was pulling the system apart, this valve had the small port plugged and did not flow in either of the two other directions, pos why I had a lot of valve cover pressure at idle... I can replace it with a two way which is what I was about to do... Is it possibly a vacuum actuated valve? so manifold vacuum opens it via the third port, and is checked upstream so this actuator port doesn't get boost

The valve in question isn't a three way valve. It's simply a check valve with an additional port on the checked side of the valve. Think of it as a check valve with a "T" attached to it. The side port is the vacuum source for the vacuum canister. If you trace the line it goes through another check valve and then it connects the vacuum canister to the N248 and N112 valves located underneath the intake manifold.

If the side port is clogged it will not be a source of a boost leak nor will it cause excessive vacuum at idle. It will simply prevent the vacuum canister from providing vacuum to the N249 and N112 when the ECM activates either of those solenoids.

[traffico]

The valve in question...

Thanks dude you're awesome!

[traffico]

Now after putting it all back together, I still have positive pressure at idle from valve cover, so... Dammit. My thought is to rebuild system with bigger hoses and valves, especially bigger valves. Thoughts?

[old guy]

How did you determine that you have positive pressure on the block? When you loosen your oil cap at idle and leave it in place the cap should dance up and down. If it sucks down hard you have a defective PCV valve. Air is displaced in the block from the pistons moving up and down and consequently the oil cap “dances” but the overall airflow will be slightly negative.

[traffico]

How did you determine that you have positive pressure on the block?

Aye mate, at idle, remove oil cap, hold hand over hole, steady positive breeze... I know there needs to be slight negative pressure there. I'll double check my lines for clogs and that I didn't install my 2-port valve in place of that 3-port valve we were talking about backwards... I may delete my suction jet brake booster valve thing just so I can use both ports on my manifold for pcv. Obv really shouldn't need both of those big lines for vacuum condition pcv but who knows maybe it'd be beneficial

[old guy]

The first thing I would recommend that you do is to replace your PCV valve. I suspect that it isn’t functioning properly. If your PCV is functioning properly and you are still operating under positive pressure at idle adding additional vacuum isn’t going to really make much of a difference. That much blow-by would be very problematic.

Haw much vacuum are you pulling at idle?

[traffico]

Haw much vacuum are you pulling at idle?

negative 18psi vacuum at idle... and i bypassed my pressure regulator valve and still have positive pressure at oil cap at idle. damn. i'm thinking i have a really worn out head but maybe its just a vacuum leak, however i don't see other symptoms of a vacuum leak that would be large enough to prevent evacuation of my valve cover... and on the upside i noticed i do develop vacuum at oil cap at approx 2000 rpms, so maybe i should just call it a really worn out engine but not like horrible. i mean the car is still fast haha. only code i get is cyl 2 misfire which is minor because it runs totally fine and which i attribute to the constant pool of oil around spark plug #2, ill do the valve cover gasket after i settle my pcv issue...

i will plug away at various other things, compression test

any thoughts on whether i'd be happy with just a new head or should i think about a whole new engine/new rings? do you know whether valve seats are going to wear out generally before rings (in a 180k engine that has been boosting 20+ for who knows how long lol)

thanks again

[old guy]

If you haven't done so you really should replace your PCV valve before going any further. If you have an '03 you should have this PCV valve: Clicky click®

[diagnosticator]

The Crankcase Pressure Regulation valve probably needs to be replaced also. The diaphragm in the CPRV gets stiff over time, and often is clogged with sludge. The CPRV is the 2" round plastic valve in the crankcase ventilation plumbing at the back end of the head.

[traffico]

If you haven't done so you really should replace your PCV valve before going any further.

The Crankcase Pressure Regulation valve probably needs to be replaced also.

The aforementioned positive pressure condition until 2000 rpms when it becomes negative is after 1) a brand new pcv valve (the one pictured in old guy's post), 2) fat new hoses in place of the oe metal tubes, 3) a new check valve from the small valve cover nipple to the tee between ccv valve and manifold AND 4) pressure regulator valve delete. (no catch can right now but that was going where the prv had been)

so i'm at either really worn out valves/seats or vacuum leak. however like i said im not getting any of the myriad other symptoms of a vacuum leak (except maybe the misfire but probably not in this case) and i'd assume that a vacuum leak big enough to let pressure out at the oil cap would be causing other problems. and don't be shy im willing to replace the head but want to know if you guys think that instead of just head i'd be obligated to do whole engine or rings etc...

and if anyone would like to instruct me on why exactly i need the prv please do, i figured with a catch can in that section, there's no real reason for it to be there. excessive vacuum is fine for the crankcase, and excessive pressure should be fine in the TIP, if it were really excessive, which it may be, then i'll just watch for my MAF getting fouled. right? eh?

gentleman thanks again. and just in case you're curious im running 415cc injectors, an unidentified ~20psi flash that came with the car, fmic, large post cat exhaust, and, drumroll, a very cheap k03

[old guy]

The PRV helps to regulate the flow of air through the block as well as the amount of vacuum whether the intake manifold is under vacuum or boost. It is a balancing act between the vacuum pulled on the PCV as well as the TIP. Eliminating it can cause excessive pull through the TIP when under boost and actually start sucking excessive oil through the intake track. It will not foul the MAF sensor since it gets pulled in after the MAF.

Increasing the hose diameters will not do anything toward increasing the vacuum. The amount of vacuum is determined by the PCV and PRV working together.

I'm still not convinced that you have positive pressure at idle. Especially if you are able to pull 18 inHg at idle. As I mentioned before if you remove the oil cap there will be air moving in and out of the valve cover at idle. The cap will actually dance up and down. If you have excessive block pressure the oil cap will not dance. It will simply blow off completely.

Here is a video that shows basically a normal condition. The person who posted the video assumed there was a problem because the oil cap danced. I suspect this is similar to your condition that you are experiencing and considering defective. If you notice that once the dollar bill is held really close to either the valve cover or oil tube the bill tends to stay down. You can clearly hear it flapping up and down when held over the oil tube.

As I previously pointed out the dancing is being caused by the air being displaced in the block as the pistons move up and down. As you increase the RPM's that in/out movement smooths out and the pulsations greatly diminish.

[traffico]

I'm still not convinced that you have positive pressure at idle...

Ha! Right u are! Closer examination, i.e. with a piece of cardboard and alternately by actually closing my palm to the oil cap hole confirms that there is in fact slight negative pressure at idle. The air movement from an inch or two away was very deceptive. Thrilled. Gracias!

On to valve cover gasket and prob suction jet booster delete

[old guy]

Yep. It can be deceptive because of all the pulsing.

Now consider putting that PRV back in place

[KHARDa4]

I have both the prv and a billet aluminum 034 pcv that are new from my build that I did not use. I ended up routing all my own lines therefore I did not need them. PM me if you're interested.