TheSamba.com :: View topic - Type 4 Oil Breather Pressure Regulating Valve 022 115 303 A

Fri Jan 23, 2009 11:32 am

I'm really glad that there is some interest in this. Like I said, I keep being told that this part is just a baffle or a right angle adaptor. The hole on top is a vacuum leak for sure because if it hook up a vacuum gauge the needle goes up a bit and stops fluttering. What is really odd is that the hole corresponds with one of the tears in the diaphragm, like maybe the shady shop I took it to (before I learned that it's best repair these cars yourself, or find a really trustworthy mechanic) drilled the hole in there to cause problems. (The same shop sent me home with the timing set at 13 degrees ATDC and a valve from a bug they said they replaced.)

I like the idea of trying to fit an available PCV valve in the breather box. I saw a few PCV grommets at the auto parts store that look like they'd fit. There are so many valves with different pressure settings though, and I'd like to be 100% sure that it is a PCV valve. It is really strange that the Bentley repair manual doesn't mention this part at all. I think that is why it has been ignored by people and mechanics.

Better yet would be if Bus Depot or some vendor could get MANN or someone to make 1000 of these again.

Fri Jan 23, 2009 1:25 pm

The hole in the top is an "engineered" vacuum leak. Some of these breathers had them an and few did not. The hole acts like a vacuum breaker. It is designed to allow air to bypass through to the manifold from moderate to light manifold vacuum without pulling on the diaphram.

The thing to remmeber about these breathers is that they have crankacase presure on one side and vacuum on the other. If vacuum gets high enough it can lift the diaphram even when there is little to no crankcase pressure to vent.

It does not mess with L-jet as bad as a PCV will with D-jet...but it can in certain circumstances wherin a litttle too much vacuu mwith a little too much blowby...causes the diaphram to lift too far dumping a big lungful of air to the intake...downstream of the metering flap. This gives a lean spot as the flap did not get to meter for this air.

Its worth it to remember. There is no reason that PCV has to be intermittant...or on and off. As long as you have a decent amount of air flow to pull crankcase gasses out...it gets done.

The problem is when on our vehciles the PCV vents to the positive vacuum side of the manifold if your airflow gets too large....you effectively have a vacuum leak that disturbs metering.
You could just as easily have a reduced (but accounted for) constant flow rate of scavenge air....instead of waiting for gas pressure to build up until the PCV is FORCED open.

Another way to put it is...why wait to have 1-cubic feet of gas build up to 1/2 atmosphere...every 4 seconds before it gets sucked out (venting to one full atmosphere)....when you can get the equivalent flow at the same 1/2 atmosphere (light vacuum)....through a fixed orifice flowing 1/4 cubic foot per minute. This is just a for instance.

On D-jet, I have gotten rid of the guts of the PCV and simply put a restriction in the line with a 3mm hole in it. I get better flow through and less idle control problems.
L-jet would need a bigger orifice possibly. The D-jet system was a flow through. One of the best I have seen.
Filtered air flows from the air cleaner, through a flame trap to each rocker box. it is then pulled through the pushrod tubes, taking case gasses out the oil breather chimmney at the top, through the PCV or orifice...into the manifold Ray

Fri Jan 23, 2009 1:27 pm

By the way...this same part is used on rabbits and golfs through about 93 at least.
you can see a picture of it in this thread
http://forums.vwvortex.com/zerothread?id=3685675 Ray

Fri Jan 23, 2009 1:36 pm

I am not sure that you can replace the L-jet pressure regulating valve (PRV) with a PCV valve without problems. I am not saying you can't, I am just not sure what problems would arise. If anyone tries this they should watch very carefully what is going on with their motors. You do not want to over pressurize or under pressurize the motor. In a standard PVC system things are hooked up differently, the PVC valve meters air from the crankcase into the intake manifold unlike the PRV which feeds to the high pressure side of the throttle body. A PVC system also has vents typically in the rockers to keep the crankcase pressure close to atmospheric.

If the correct PVC valve were used directly in place of the PRV and plumbed the same to the high pressure side of the throttle body the PVC valve might work fine. The weight of the plunger in the PVC valve would tend to cause some back pressure to build up in the case (but maybe too much?). With the existing L-jet system, extra suction from the intake air would cause the PVC valve to open more whereas extra suction should cause the PRV to close. This to me would imply that you were more apt to have a vacuum drawn on the crankcase if you used a PCV valve verses a functioning PRV, the vacuum shouldn't be very high though just what ever vacuum is drawn by by the AFM and the air cleaner at full throttle.

That said a PVC valve might be better than a non functioning PRV in any case. The PRV tends may fail either fully open or shut. Either extreme would cause problems. I tend to think that gutting the valve and using Rays orifice system might be the way to go. Note that the original valve does not appear to me to be an affective backfire valve whereas a PVC valve would be. It looks like PRV valve would just blow open if there were a backfire. No telling what VW's thoughts were here.

Fri Jan 23, 2009 2:02 pm

raygreenwood wrote: The hole in the top is an "engineered" vacuum leak. Some of these breathers had them an and few did not. The hole acts like a vacuum breaker. It is designed to allow air to bypass through to the manifold from moderate to light manifold vacuum without pulling on the diaphram.

The thing to remmeber about these breathers is that they have crankacase presure on one side and vacuum on the other. If vacuum gets high enough it can lift the diaphram even when there is little to no crankcase pressure to vent.

It does not mess with L-jet as bad as a PCV will with D-jet...but it can in certain circumstances wherin a litttle too much vacuu mwith a little too much blowby...causes the diaphram to lift too far dumping a big lungful of air to the intake...downstream of the metering flap. This gives a lean spot as the flap did not get to meter for this air.

Its worth it to remember. There is no reason that PCV has to be intermittant...or on and off. As long as you have a decent amount of air flow to pull crankcase gasses out...it gets done.

The problem is when on our vehciles the PCV vents to the positive vacuum side of the manifold if your airflow gets too large....you effectively have a vacuum leak that disturbs metering.
You could just as easily have a reduced (but accounted for) constant flow rate of scavenge air....instead of waiting for gas pressure to build up until the PCV is FORCED open.

Another way to put it is...why wait to have 1-cubic feet of gas build up to 1/2 atmosphere...every 4 seconds before it gets sucked out (venting to one full atmosphere)....when you can get the equivalent flow at the same 1/2 atmosphere (light vacuum)....through a fixed orifice flowing 1/4 cubic foot per minute. This is just a for instance.

On D-jet, I have gotten rid of the guts of the PCV and simply put a restriction in the line with a 3mm hole in it. I get better flow through and less idle control problems.
L-jet would need a bigger orifice possibly. The D-jet system was a flow through. One of the best I have seen.
Filtered air flows from the air cleaner, through a flame trap to each rocker box. it is then pulled through the pushrod tubes, taking case gasses out the oil breather chimmney at the top, through the PCV or orifice...into the manifold Ray
My brain just exploded!

Fri Jan 23, 2009 2:16 pm

:shock: Sorry for the exploded brain!

In most cases I have seen VW had seperate arrangements for flame trap from PCV. For example...inside of the rabbit/golf valvecovers is a flame trap grate. On VW 411/412 with D-jet and a PCV valve, there is a separate grate style flame trap installed in-line where the PCV hoses split to the heads.
A perfect flame trap could be made with a 1" diameter chamber filled with some of those wadded up"chore-boy" style aluminum or brass scrubber pads. They have almost "0" blockage ability and are almost identical to whats in a flametrap. Ray

Fri Jan 23, 2009 2:32 pm

The valve part number for the later VW's is 028129101D, which is about $55. I might try to get ahold of one of each, the old and new to see if the diaphram from the new one fits the old model. (Expensive test). If it does and the newer ones are still being made, we might be able to find the manufacturer and buy a bunch of diaphrams and create a kit so people can repair their old ones. The top would have to be welded back on in a way that it could not seperate later.

On the subject of the small hole on the top. My unit holds vacuum between the tube and bottom with that hole left open. It could be that crud has plugged a bleed hole in the diaphram, but I am more inclined to believe that the function of that hole is to allow the diaphram to move without building pressure between it and the cap glued over it.

I do agree that Mann or Fram or someone needs to make these again.

Sat Jan 24, 2009 2:59 pm

raygreenwood wrote: By the way...this same part is used on rabbits and golfs through about 93 at least.
you can see a picture of it in this thread
http://forums.vwvortex.com/zerothread?id=3685675 Ray
So are you saying we can get this part from our dealership and use it?

Sat Jan 24, 2009 3:10 pm

SGKent wrote: To anyone who has had one apart. (1) Does the spring sit above the diaphram? (2) does the center of the diaphram seal the top of where the tube enters the body?

If so then the small hole on the bottom allows the metering of blowby in the closed position. If pressure builts it would push the diaphram up and open the larger hole to allow a greater flow. The tiny hole on the top would be to allow the backside of the diaphram to vent to ambient pressure.

Mine is apart and was messed with prior to my ownership (lots of RTV on the seal and around the cap). Yes, the sprind sits on a perch and it surrounds the tube that allows excess pressure to go into the intake. The diaphragm rests on top of the spring. So the spring is actually pushing the diaphragm AWAY from the port that vents excess pressure. My guess would be that the vacuum of the intake actually pulls the diaphragm shut, thus only a tiny amount of case gases are pulled from that tiny hole (what someone suggested as a drain):

When case pressure is greater than the vacuum pull against the diaphragm, it gets ingested and the diaphragm closes once again, like Ray explained. So it's "fail-safe" mode (if you want to call it that) is to keep that port open.

Sat Jan 24, 2009 3:16 pm

no - what I am saying is that it looks to be the same design and size but it mounts different. If so one may be able to take the diaphram out of the newer style and use it to refurbish our style. I just bought 3 vanagon style aircooled valves that are 2 1/2" across the top. If the diaphram is the same then I can rebuild my bus one.

Sat Jan 24, 2009 3:24 pm

I just took some pictures of mine. Gimme a few minutes to download 'em and post 'em.

Sat Jan 24, 2009 3:47 pm

Spring on the perch, surrounding the purge tube that vents pressure to the intake. In the center of the diaphragm you can see where the spring sits:

Loosely assembled:

Light shining through the purge tube (top view):

Light shining through the drain hole(?) (bottom view):

These images can be found in the gallery under Parts/Accessories - 68-up Bus.

Note: If any of you volks quotes this post, please remember to edit out the images you don't need as it helps to speed up page loading, especially for those of us who surf the web on our PDA/smart phone ;) Thanks!

Sat Jan 24, 2009 4:09 pm

I'm cornfused. Does it open and close anything or just smooth out the pulses? I can see how the tiny hole on the cap allows atmoshpheric pressure to be nil

Sat Jan 24, 2009 4:10 pm

I think I was missing what this valve actually does. A regular PCV valve regulates airflow from the crankcase into the intake, and shuts it off at times when it would adversly effect the A/F mixture and H/C levels. A regular system ususally has a breather that allows excess pressure to still vent to the air intake even when the PCV is not scavaging the crankcase. A regular PCV system monitors vacuum levels AT THE INTAKE.

This system is designed to monitor vacuum levels INSIDE THE CRANKCASE and shut off vacuum to the crankcase when it gets too much. Too much vacuum in the crankcase pulls the diaphram valve closed which turns off all vacuum except through the bleed hole. Any time pressure builds back to preset / neutral level then the valve opens and more vacuum is applied. It is not a true PCV system as it is not controlling crankcase ventilation but rather it is controlling crankcase internal pressures.

Gutting the unit and installing a bleed orifice might work but it will not solve the problem as VW percieved it. It appears that VW engineers wanted full vacuum at all times except when there was excessive negative pressure in the crankcase.

To calculate the negative pressure this valve was designed to close at, I think the calculation would be

(Pressure of collapsed spring when closed) = [(surface area of diaphram) X (vacuum psi to close it)] . Since the pressure to collapse the spring can be measured, and the size of the diaphram is known, the PSI in vacuum could be calculated.

From this one could assess what VW Engineers saw as a maximum vacuum in the case. If one went to an orifice system one would simply need to choose an orifice that barely never allowed vacuum to exceed that.

Sat Jan 24, 2009 5:19 pm

regis101 wrote: I'm cornfused. Does it open and close anything or just smooth out the pulses? I can see how the tiny hole on the cap allows atmoshpheric pressure to be nil
From what I'm seeing and the fact that the spring is very mild (compresses VERY easily) I would guess that the device is meant bleed off excess pressure from the case, thus the case would tend to have positive pressure and not negative. Excess pressure would push the diaphragm UP, thus opening the hole on the purge tube and allowing the pressure to escape into the intake (which is after the metering vane).

SGKent, why do you think it's meant to keep the case at a negative pressure?

You know, I don't know what the vacuum is at the point where the case fumes bleed into the intake. I'm under the assumption that it would be a relatively high vacuum but I could be wrong.

Sat Jan 24, 2009 5:48 pm

It doesn't keep the case at a negative pressure, it PREVENTS EXCESSIVE negative pressure by reacting to negative pressure. It doesn't care how postive the pressure gets.

there are two sides of the diaphram. One side faces a vent hole that goes to outside / ambient air pressure.

The other side faces the inside of the crankcase. At rest the diaphram is out as far as it can go. Adding positive pressure in the crankcase can't push the diaphram any further because the spring already has it pushed against the top that has the hole to the outside. The only thing that can move the diaphram is vacuum from the engine

However when the vacuum moves it against the spring, eventually excessive negative pressure pulls it down to where it seals that nipple that sticks up, thus cutting off vacuum to the crankcase from the hose.

Then the only vacuum that can reach the crankcase is through that tiny hole on the bottom.

The path when it is open is up from the bottom around and out the nipple. Negative pressure in the crankcase closes this route.

Sat Jan 24, 2009 6:48 pm

Ok, I understand what you're saying. We're on the same track.

Sat Jan 24, 2009 8:15 pm

it occured to me that we might be saying the same thing but from a different perspective. I am not always at my best explaining things.

Mon Jan 26, 2009 2:22 am

Those pictures of the bus valve posted by "air cooled nut" are great.

So the tiny hole in the top cover of the valve is original to the design to allow the diaphragm to move freely, without any impedance from the closed area created by the cover? However, if the valve diaphragm ruptures, then there's a vacuum leak through that hole?

Also, I have seen the metal "decel" valve (air enrichment, smog valve) being called an anti-backfire valve. I don't think this one being discussed has anything to do with backfire.

The MANN website has a picture of what looks like our crankcase pressure regulating valves http://www.mann-hummel.com/crankcaseventilation/index.html?iKeys=19.1.236.1.1

They should be able to make some of these up in no time at all. I wonder how many busses there are anymore that need this part? I wonder how much less oil a bus engine would burn and how many less leaks there would be?

Mon Jan 26, 2009 8:07 am

Quote>>>>A regular PCV valve regulates airflow from the crankcase into the intake, and shuts it off at times when it would adversly effect the A/F mixture and H/C levels. Quote>>>>

It does nothing of the kind. It has no mechanism or logic componet to allow it to shut off and on to keep it from adversely affecting A/F mixtures and CH levels.
It opens and closes by a combined level of vacuum on one side of the valve(on some models in some engines) and crankcase pressure on the other.
Since there are no sensors to measure crankcase pressure and it varies on every engine there is also no way to really accurately regulate this by spring pressure alone in the valve.
Since this valve on these engines goes to the air cleaner and not the manifold...its probable that vacuum is not really as big of a factor in valve opening as it is in the type of PCV valve that is used on the 411/412 and 914.....but...I can't be sure of that.....because....as diaphrams get larger they have more surface area. The larger the surface area the more influence a small amount of vacuum or pressure has. Diaphram size is a leverage multiplier.

The diaphram in this valve is roughly 15-20 times the size of the diaphram area in a 411/412/914 PCV. The PCV in a 914 or 412 sees at most 15-18" hg. This one may see what.....1-2" hg?....but at 15-20 times the size of a valve seeing 15-18" hg.....then perhaps vacuum does have effect. I would have to measure it.

In short, PCV's of all types open at will whenever there is enough combined vacuum and crankcase pressure to cause them to do so. There is no logic or control to it.

I actually used to think that American PCV valves were a rather sad crappy design. Some early ones were. After going through the trials and tribulations of the PCV system on the 412....which has serious issues for D-jet.....partly because when D-jet was designed...there was no requirement for PCV...and it probably vented to atmosphere...so it was an afterthought......anyway...after this...I took a better look at American style PCV's...and found that some were quite well designed.

In the crappiest ones...you find a weight block or plunger. Vacuum has nothing to do with these. The gram weight is usually stamped on the bottom of the plunger. The amount of crankcase pressure a given engine in new or good shape produces...is what dictates what pCV valve number you used. That worked pretty well except that the PCV weight has a habit of jiggling up and down on bumps and unseating....so again...no real logic to how and when it vents. But...since those just went to the air cleaners...who cared? It would not upset your vacuum signature.

As later cars started using PCV's hooked to manifold vacuum instead of just routed to the air cleaner ....It took me a while to figure out in the old days what the mechanics were doing when you brought your older slightly worn out car to them when it would not pass emmissions....and they said you needed a new PCV valve...when you has just replaced it shortly before :? . Since you now had more blow-by from the pistons...they were...simply swapping in a similar PCV that had a heavier weight....or a later one that had a light weight and a back-up spring that would not vibrate when going over bumps. Ray