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Tue May 13, 2008 9:21 am

Actually, as poor as the design may seem, it does work when it isn't deteriorated. PCV valves are a fairly unreliable items, and they are scheduled for frequent replacement in most cars. Even the BMW ones on my Range Rover have died within 6 years, as did the hoses that went with the system. They got soft and collapsed and turned gummy. In fact they did the same as that little piece of hose did on my tower when I first got the van! I do think it lets too much oil vapor out, as my oil consumption is a bit on the high side with the 2.4L. I know it is blowing the oil, as it does the first quart over the side in a hurry, just like my airplane.

The Airplane does have an Air Oil Separator. I don't want to know how much oil I would lose without it. I checked, and the Walker Air Oil Separator costs a measly $495. That is a lot of oil! So $88 for a new breather tower looks pretty good now. So 20-25 years for a weird PCV valve isn't so bad, it is more than twice the longevity I have seen in the conventional ones. It would be interesting to put the Mason Jar idea on the breather line to the intake and see how much oil you can recover.

Tue May 13, 2008 9:33 am

I don't know that the jar concept is so much oil recovery as the other liquids that otherwise end up coating the intake tract. There's surely some oil in there, too, but I doubt it would be reusable, as it would be pretty acidic with dissolved carbon. It's just a way to keep some of the coarser crud out of the engine, as I understand it. The systems you use on the planes are obviously much more sophisticated, but then my van doesn't normally veer very many degrees off the horizontal like an airplane can do.

Seems like they did try to limit flow with the 5mm restriction on the line.

On other cars, PCV valves are positioned for easy service and are specified for frequent replacement. Just a regular tune-up item, to do with the air filter every year or two. At $6 a pop, I could live with that, and it's easy to take them off and check to see how gummed up they are. I see that level of serviceability as a plus. Sure, the VW design worked fine when new, and it lasts awhile, but at 20 years old, how long has that thing already been inoperable, really?

Tue May 13, 2008 10:10 am

Yes I do wish the British used $6 ones like many US built cars, alas its $27. The level of sophistication you describe for the air oil separator in airplanes is unworthy of the actual device. It is a CAN! The high price is all due to paperwork. Our lovely and criminal FAA. So many items on this Van are a little proud of themselves, price wise. Then again, it could be a Japanese car. If you go to Africa, you will see loads of Toyota Land Cruisers, but if you look closely, you almost never see old ones. Loads of old Land Rovers, no old Land Cruisers. Parts are sky high. They can strip a dead Land Cruiser so fast they put the New York types to shame.

Tue May 13, 2008 3:15 pm

I dug out an old Gunson Gastester leftover from the motorcycle days and hooked it up to the Westy. Interesting. I disconnected the CC breather hose and clamped the hose shut, started up the motor and noticed:
1) the disconnected cc breather valve makes a lot of noise, dud-ah-dud-ah-dud-ah.....like a valve opening and closing (flapping)
2)the afm contact arm is nice and calm with the cc breather disconnected. Connecting the breather hose causes the afm arm to thrash around in sync with the dud-ah-dud-ah..... That thrashing around can't be right and probably contributes to the poor idle.
3) capping the disconnected breather valve stops the valve-flapping noise but has no effect on the CO reading. Someone was wondering if allowing air into the crankcase would affect the fuel mixture, I guess not.

I've gone ahead and ordered a new breather valve. I don't think it will solve my poor idle but it will be one less thing to worry about.

A couple of questions came up in this process:
1) does the VW crankcase volume change a lot as the motor turns over?
or does most of the "breathing" come from blow-by?
2)Is there a simple relationship between exhaustpipe CO readings and (disconnected) O2 sensor voltages? I couldn't get them to correlate.

Cheers,
Charlie

Tue May 13, 2008 4:54 pm

The volume shouldn't change much, as one piston is decreasing the volume, another is increasing it, they tend to cancel each other out.

I love the Gastester a blessedly simple device to set your CO (and cheap to, about $100-150). Personally I never checked the O2 sensor against it, never thought to. It would have been interesting. 10¢ point about using a virgin 02 sensor, of later design, may give more accurate readings.

Keys to a good idle 86 and newer(others add to the list please)
1. Throttle Switch working as it should
2. Timing set properly
3. Idle Control Valve and idle screw relationship set properly (the idle is set, then the valve is set to its mid point electrically)
4. No vacuum leaks
5. Good ignition system
6. Non-worn out throttle valve
7. Working Idle Control Unit
8. Working Temp II
9. Properly working Fuel Pressure Regulator
10. Non-blocked Cat
11. Throttle plate returns to its closed position every time, no weak springs or hanging cables
12. I suppose we should add the breather tower working as it should

Tue May 13, 2008 6:05 pm

So, Chris, can you discern anyway to test the function of one's breather diaphragm without cutting it open? Could you pull vacuum on it to test?

$88 is an expensive method of troubleshooting...

Tue May 13, 2008 6:08 pm

Dogpilot wrote:
3. Idle Control Valve and idle screw relationship set properly (the idle is set, then the valve is set to its mid point electrically)

DogPilot, can you explain this a bit more? Is the electrical part in the Bentley?

Tue May 13, 2008 6:48 pm

Yes I suppose that was a little simple for what is a rather involved procedure. If you have the timing set correctly and the Throttle Switch working like it should, you can do the idle set up. It is pointless to start unless your sure the vacuum system doesn't leak, the Idle Control Valve is clean and your Fuel Pressure Regulator is working like it should (yes and the breather system is working).

When you set the CO it makes the idle speed change. So you have to go back and forth. You get the CO in range, adjust the idle screw, observe the Milliamps on your meter. Check the CO, adjust the screw and so forth. If you get it correct, the valve is more or less in its neutral position, able to add and subtract equally in both directions.

A quick test would be to suck on the hose to the breather, you should be able to tell if the diaphragm closes. A long clean hose would be best, and oh yeah, the engine off.

Fri May 16, 2008 7:22 pm

RHPAW, did you get the new breather installed, and did it fix the problem?

Sun May 18, 2008 12:58 am

Dogpilot wrote: The volume shouldn't change much, as one piston is decreasing the volume, another is increasing it, they tend to cancel each other out.

I love the Gastester a blessedly simple device to set your CO (and cheap to, about $100-150). Personally I never checked the O2 sensor against it, never thought to. It would have been interesting. 10¢ point about using a virgin 02 sensor, of later design, may give more accurate readings.

Keys to a good idle 86 and newer(others add to the list please)
1. Throttle Switch working as it should
2. Timing set properly
3. Idle Control Valve and idle screw relationship set properly (the idle is set, then the valve is set to its mid point electrically)
4. No vacuum leaks
5. Good ignition system
6. Non-worn out throttle valve
7. Working Idle Control Unit
8. Working Temp II
9. Properly working Fuel Pressure Regulator
10. Non-blocked Cat
11. Throttle plate returns to its closed position every time, no weak springs or hanging cables
12. I suppose we should add the breather tower working as it should
Edit:
8. Working Temp II AND THE SOCKET CONNECTED TO IT. ( I had them fail on two cars one winter.)
and :
13. Intact and cleanly connected ground straps between the head and the chassis.
(this should be nearer the top, actually.)
Al

Mon May 19, 2008 7:53 am

Yellow Rabbit wrote: RHPAW, did you get the new breather installed, and did it fix the problem?
Like a champ..
I got the package Thursday evening. Friday morning I was scheduled to head out to the great Colorado Sand Dunes at 5am. The Wife was pretty pissed when she came homefrom work and found me in the engine bay instead of loading the van.
"you're fixing WHAT.. NOW??"
--chicks!
Anyway, I was hoping to find a smoking gun in the old breather, I pulled it off and blew through both ends looking like I was inventing a new improved way to smoke weed.. -no resistance from either end. -HA! obviously this is the problem!
Out of the box comes the new breather. I smoke it in the same way.. -same feeling, no resistance either way.. -not what I had been hoping.
I hooked it up with new gaskets and tube anyway and buttoned the system back up.

Startup proved well, and idle is now rock solid... The van logged over 400 miles this weekend. Gas milage is up to around 21, power was good through the passes and temp was completely solid on the low side of the LED all trip.

I'll tear apart the old breather when I have a chance.

This was a failed part on my system, replacing it helped immensely.

Mon May 19, 2008 8:12 am

You would never be able to pull enough vacuum on even a new one to close the diaphragm valve, so free flow in both directions by mouth is what you would see. Not a way to tell if one is bad because a bad one would act the same as a new one.

It's great to hear that replacement has such good effects, though. Kind of shocking, actually. VW has an 88-dollar PCV valve, and it's totally inferior in design to the $6 ones American cars use. I never thought the day would come when I would say that the Americans got something right, but the day is here.

I looked into the design of PCV systems on various cars, and it seems like the Euro makers do it passively, while American cars, and Japanese, have an active flow-thru system, by and large. That stems from the fact that unburned HC as a contributor to smog was discovered here, and PCV systems were the first emissions control mandated on cars, according to Wikipedia.

And gumming of the PCV rattle-valves found atop most motors doesn't seem to be a problem in reality. I can't recall ever changing one out that actually needed changing. They are designed to be kept lubed by the oil mist that passes thru them, and I believe that that works for the most part. Not perfect, but far superior to a wanky diaphragm valve that rots out and can't even be inspected. Just shell out the 88 bucks, on schedule. Except there's no schedule. It's supposed to work forever. Go figure. Thanks VW!

You must have looked pretty funny with your lips all smooched up into that big hole in the base, though. I would have paid to see that. Unless you managed to get your mouth around the base instead. I would pay NOT to see that!

Mon May 19, 2008 8:18 am

tencentlife wrote: You would never be able to pull enough vacuum on even a new one to close the diaphragm valve, so free flow in both directions by mouth is what you would see. Not a way to tell if one is bad because a bad one would act the same as a new one.

It's great to hear that replacement has such good effects, though. Kind of shocking, actually.

You must have looked pretty funny with your lips all smooched up into that big hole in the base, though. I would have paid to see that. Unless you managed to get your mouth around the base instead. I would pay NOT to see that!

So, I take this to mean then that one can't really test the function of this device?

I would have thought that too much vacuum pressure was a risk - tearing the diaphragm.

Mon May 19, 2008 8:20 am

yeah.. I imagine it looked rather odd.. My neighbor is a cop, and already has interesting looks that he gives me. Pulling random parts from the back of my hippievan and puffing on them like a pipe probably doesn't help.

The breather was fixed was in conjunction with a bad t-stat just a week prior.. Both being replaced is what gave me such great gains.

Mon May 19, 2008 8:27 am

mordeaux wrote:
So, I take this to mean then that one can't really test the function of this device?

I think the best way to test the system is to just bypass it. If you're having idle / running issues, just pull the hose running to the intake boot and cork the boot hole with your thumb.

If your idle steadies, and you can goose the throttle and everything seems "better" you probably have an issue.

Mon May 19, 2008 2:38 pm

Just want to drop in for some info on the breather tower. Mine is pretty beat up so i called about a new one. Dealer told me there are 2 in the country. Don't know if that means no more coming. I think van cafe still has them.

Tue Jul 15, 2008 4:45 pm

This is a very interesting thread on the subject of crankcase breather towers; thanks to all the contributions, especially the photos of the actual innards.

It does seem though that quite a lot of confusion still is being passed around, with regards to how the valve operates. From the photo, as well as by observing the connections from tower to inlet rubber boot, it would seem that the valve operation is never, ever going to be directly affected by the engine inlet vacuum. That vacuum is to be found downstream of the throttle butterfly, in the plenum chamber and manifold pipes; but the tower breather valve will never will see that vacuum. Rather, the hose from the tower attaches to the rubber boot located between the throttle valve and the Air Flow Meter, and will see only slight depression from ambient atmospheric pressure. It is certainly not intake vacuum that overrides the spring pressure on that diaphragm, but more correctly it is the increased positive pressure from the crankcase. True, the crankcase pressure will increase as the manifold pressure is falling, but it is the former which takes the diaphragm up, against the spring and opens the valve.

The reason that one would not be able to suck or blow against the tower and feel resistance, is simply because the valve is never fully closed – there is always the “idle orifice”. I consider that the orifice is the primary crankcase vent, and the spring diaphragm is provided to open when needed to preclude excessive crankcase pressures at high RPM (and the oil leaks and sludge problems which would follow). Certainly as the engines age and piston blow-by increases, the actual engine RPM needed to force the tower valve open will decrease. The valve will open at lower power settings as an engine ages, regardless of the vacuum pressure in the intake manifold.

A failed diaphragm in the tower valve will approximate the situation of a fully open vent at all power settings. Thus at idle such un-metered flow from crankcase directly to the inlet boot will surely have a negative effect on one’s efforts adjust idle mixture and idle speeds. This will only be made worse it the engine is a high-mileage specimen, with the extra blow-by.

At least this is the way it looks to me. That posted diagram, with references to vacuum operation of the valve, can likely be put down to poor translation from the German.

Tue Jul 15, 2008 7:06 pm

Your theory would make perfect sense, JW, if the spring was positioned above the diaphragm and pushed it down onto the J-tube. But the spring is below the diaphragm and pushes it up off the end of the J-tube. That means that the valve only closes off if vacuum is very high on the breather hose over to the intake boot. I concur, though, that vaccum there is only going to be at all substantial at mid-throttle cruising conditions. There is zero vac there at idle, and zero at WOT. I've made measurements that confirm this.

In addition, there is no venting above the diaphragm, so differences in pressure below it vs. atmospheric play little part.

It's still a mystery to me how this thing is intended to work.

About the only thing that makes good sense is the warmer on the breather line, to prevent icing of the water-laden vapors when it's cold. That part I can get my mind around.

I'm envisioning a system to replace this with that would emulate the American style of PCV system: install vent nipples on top of both valve covers. Take off from the nipple on the intake boot with a tee that routes metered air to both valve cover vents. Put a common PCV valve inline on the hose off of the breather tower, and lead a hose from there directly into the manifold plenum. Put the warmer inline below the PCV valve.

That way, metered air from after the AFM would split and flow into the valve covers, down the pushrod tubes into the case and exit the case at the tower, where the separator baffles can help get the liquid out. The PCV valve would regulate the flow thru this network, restricting it at high vacuum such as at idle and cruise when blowby is the least, and opening it to higher flow at WOT when blowby is the greatest.

Tue Jul 15, 2008 7:27 pm

:idea: lotsa performance air brothers have the valve cover breathers on those setups.
Time to mod the vent AND the dizzy plug.

Tue Jul 15, 2008 7:37 pm

What's the dizzy plug have to do with it? Or are you just airing out your to-do list?