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Thu Jul 17, 2008 11:02 pm

Wildthings wrote: Too bad new ones cost so much, I would like to dissect a new one and see what they are supposed to look like inside. Any one feeling rich?

nope. my new one is supposed to arrive tuesday. it will be directly put to work.

Fri Jul 18, 2008 11:58 am

Well there were no surprises in replacing the breather tower. With the new tower in, the idle RPM and running were unchanged, as I expected.

Before changing the unit, I did plumb in a vacuum gauge to the rubber intake boot just to confirm my expectations. I ran the van on a road test through all power settings from idle to FOT and never did the vacuum indicate above zero. I know that there actually is a slight depression in that boot but it was never enough to indicate on my dash vacuum gauge. Back home I put on a slightly more sensitive Snap-On gauge, but still all I could see was a slight wiggle in the needle……..less than half a pound.

I am where I started with this tower issue, and believe that those who report improved idle performance after replacing the breather must have actually corrected either an air leak problem or perhaps (unlikely) a fully clogged tower exit pipe. In short, the new tower has a functioning valve, spring loaded open – but it will never see sufficient pressure differential to close it. I don’t see any reason to buy a new tower unless yours is cracked or so clogged up that air will not flow freely.

Don’t really know about posting photos on this forum, but I will try. First is a look inside the top of my old tower after the top was cut off. This breather has better than 250K miles on it, being the original from 1984.

The hole at the bottom of the outlet pipe is solid with crud and not even oil would pass through it.

This is the top section and the diaphragm is all but gone to pieces. I did blow through the square vent hole before cutting the top off, and I knew the diaphragm was bad because I could hear air blowing right through the tower.

This next photo is all I could retain of the original diaphragm.

And I show this view because you can see at the tip of that scribe the slot in the plastic top which communicates the square vent hole with the upper diaphragm chamber.

Fri Jul 18, 2008 2:18 pm

Urp! I was eating my lunch when I saw these pics. Lost my appetite, I did. Yuck.

JW, I have a NC vac switch that is calibrated to about 2"Hg and it opens the instant the throttle tips in, so I can definitively say that there is at least that much vac in the intake boot between off-idle and WOT. I have indication of its function up front by an LED, so I've been able to monitor how it's working for a few months now. I doubt it's a lot more than 2", though, because the LED lights again when engine loading is only moderately heavy. This is at 5-7k ft. altitude as well; the vac depression relative to ambient would be quite a bit greater at low altitude.

Maybe to correlate with my vac observations, since you have a nice new tower handy, you could block off the bottom, and rig a vac pump/gauge combo, if you have one, on the outlet pipe to see how much vac causes the diaphragm valve to close. That would be useful info in figuring out how the thing is expected to work.

I gotta take closer look at my dissected tower. I did notice the notch at the edge of the diaphragm and thought it was perhaps a way to vent air to the top, but I couldn't see where the air was routed from. My specimen was much much cleaner than JW's nasty little critter there, but perhaps I chewed up the top so much in cutting it open that the air routing was obscured.

Fri Jul 18, 2008 4:49 pm

Hi tencent,
So sorry to have ruined your lunch. Remember that this tower is one of the really old ones, and likely the worse we can expect. 250 K miles is actually only a guess, because the speedometer was inoperative for several years. Probably it is well over 300K.

Since that last set of photos worked so well I will offer a few more. To find the hole which vents the upper chamber to ambient, look under the upper lip. I noted that it was square shaped on the new tower, but on the original it is round. Both are in the same location however.

And the same view from a little closer in.

This photo is from the top, with a sheet of paper to show up the vent drilling.

Now, what exactly is a NC vac switch you refer to? I just don’t understand the term, and I wonder if it is working correctly. What I plumbed into was the rubber boot line which usually connects with the cold start valve, because it is on top and easier to get at. To be sure there could be no issues with possible leakage at the cold start valve, I plugged that line and took my readings right from the rubber boot. Altitude here is about 2500. Sea level would certainly be different.

For certain, the rubber boot is not exactly a venturi, but more like a balloon. The air passing through will still tend to drop the pressure though, and I wanted to measure it. At the same time we need to remember that the rubber boot is also open to the crankcase pressure, which will be slightly positive to ambient. As the boot vacuum goes up with increased throttle opening the opposite will be happening in the case where blowby will also increase with higher RPM. The two will tend to cancel each other, though neither is very strong in the case of a sound engine. (This engine has maybe 15k miles since rebuild with new heads and new p/c. It does not use oil between changes.) While they will tend to cancel, I would expect vacuum would increase overall. Very small forces though.

The dash gauge I have is an ordinary VDO vacuum gauge which is normally recording plenum pressure. In that case, the highest vacuum is not at idle, nor even at partial throttle. The highest spike in vacuum will occur just after suddenly closing the throttle, under load, after FTO. Full throttle vacuum again will of course be zero on the gauge (but not in fact, as there is always resistance in the intake/ filter/etc.).

When I used the more sensitive diagnostic gauge on the engine at idle, I could read about ½ pound vacuum. I only did it at idle, and probably at cruise throttle it would amount to 1 or 2 pounds and perhaps three or more under full throttle back-off. Maybe in those cases the tower valve will actually close!

I didn’t think to attempt your suggested test of measuring exactly what vacuum will close the valve. I doubt tencent, that such a test would be meaningful, because as I mentioned in an earlier post, when you close that valve with vacuum all you have for evidence that it closed is the very faint feel through your fingertips on the plastic lip. I other words, you need to sort of slam it home to feel that it has moved. To get a real value we could use………no I don’t think I could do it.

Regards, and hope these images haven’t spoiled your dinner as well.

James

Fri Jul 18, 2008 5:06 pm

Might be interesting to put a U-Tube Manometer on the case with both a used and new breather tower. This would show the affects on case pressure. My 84 is probably not a good candidate though with its high blowby and oil use. I can't imaging the blowby would ever let the valve close.

Sat Jul 19, 2008 2:22 pm

I want to order a new crank case breather, but I tried a couple places....no go....

know where I can buy a new one????

Is it possible to take out the old one and clean it????

if so, how does one go about cleaning it???

Sat Jul 19, 2008 6:11 pm

weatherbill wrote: I want to order a new crank case breather, but I tried a couple places....no go....

know where I can buy a new one????

Is it possible to take out the old one and clean it????

if so, how does one go about cleaning it???

I ordered one, but after reading the last posts, it appears it doesn't do anything, or at least doesn't have anything to do with my idling problem.

Volkswagen dealers should be able to get one for you.

Sat Jul 19, 2008 8:01 pm

weatherbill, I got mine last week from Van Café’. Go to Van-Café.com and type breather tower in the search engine.

I hesitate to suggest that a new breather tower is probably not needed. I just put a new one on my engine, and while I don’t think it improved engine operation in a measurable way, it does comfort me to know that that mess of rotted goo in the old tower top is no longer with me. That is, the risk of a clogged pipe in future is greatly reduced. That said, and knowing what I know now, I might have just left well-enough alone, kept the money and spent the time elsewhere.

You can of course take the old tower off and slosh a degrease solution around in there. Probably anything loose will come out. I probably did exactly that during my last overhaul and you can see from the photos just how effective it was. The problem is that you cannot see beyond the baffles in the tower and cannot know how clean it is or isn’t in the top section. That nasty example of mine in the photos is probably about as old as they come and in spite of the terrible mess of goo up there, it was all firmly in place and did not significantly alter the flow through the tower. I also expect that is likely to be the usual failure mode of the diaphragm. When they rot out, most will fail OPEN.

If yours is free and clear as you blow into the outlet pipe, and there are no cracks or deformation which might cause air leaks, then probably it is not causing your idle problem.

One opinion only.

Sun Jul 20, 2008 12:21 pm

Quote: The problem is that you cannot see beyond the baffles in the tower and cannot know how clean it is or isn’t in the top section.

Well this was one item you may not have noticed, and someone else upthread asked about how to inspect the thing as well. The baffle is a separate part and comes out easily from the bottom once the tower is removed. Then looking up from the bottom you can see almost the entire diaphragm, the only part not visible being where the view is blocked by the J-tube.

JW, I did go back and took a closer look and found the air orifice that you pointed out in your photos. Thanks for those. I was looking on the top cap or along its rim, so I missed where they turned to route downward and out under the rim. To be honest, my hacking off of the top messed up the area where I might have noticed this from the inside. But sure enough, there is a tiny hole there under the rim. On the one I hacked apart and another intact one, the orifice is completely blocked by dirt, though. On the intact one, I looked up inside and the diaphragm appears to be complete. I cleaned the dirt out of the orifice. But when I block off the bottom with a sealed plate, and draw on the outlet tube, I can hear air being drawn in the orifice, so that diaphragm is also leaking. So even though a visual inspection from below may show an apparently intact diaphragm, a pull of suction may show it to be broken anyway.

Quote: Now, what exactly is a NC vac switch you refer to? I just don’t understand the term, and I wonder if it is working correctly.

NC means Normally Closed. I'm using a very sensitive adjustable vacuum switch in NC mode as a replacement for the mechanical TB switch or switches used on the stock throttle bodies. I've written about it in the thread about my custom throttle body and elsewhere. And yes, it is working very well as designed. I prefer not to tout my own work, but I will say it is far superior in every way to the OEM arrangement. I'm offering it as a kit, or it's included with one of my TB's.

The way it works is it is plumbed into the TB port that gives the EEC control valve signal, which would in the old school be known as throttle vacuum as opposed to manifold or plenum vacuum. Manifold vac is after the throttle; throttle vac is just upstream of the throttle. As you know, there is no vac there at idle, vac is created there as soon as the butterfly tips in, and vac varies with load, going back to essentially zero at WOT. So in place of the OEM switch, the vac switch closes the TB switch circuit at closed throttle, opens it at tip-in, it remains open at all mid-throttle operation, but closes again at or near WOT when manifold pressure increases again to near atmosphere. So it operates as a proxy for the OEM switch, but is far more responsive at tip-in, for enrichment it responds to actual load rather than just to throttle position, and isn't subject to the high mechanical wear of the poorly-designed OEM TB.

The one I have in mine is bench calibrated to open above 2"Hg. For my experimental purposes, rather than close the 5V TB switch circuit directly, the vac switch grounds a 12V relay coil and simultaneously an LED circuit up in the dash. The relay then closes the 5V circuit for the ECU. That way, I can see exactly when it's opening and closing by watching the LED.

So anyway, it does give me an indication of vac within the intake boot while I'm driving, inasmuch as I can tell when it is more or less than 2" Hg. So that was what I was talking about before. There is more than 2" Hg. vac in the intake boot from tip-in to moderately high engine load.

Sun Jul 20, 2008 1:16 pm

Thanks tencent,
I just went out and pulled the baffle from that old tower. That changes everything. Yes, it certainly is possible to effectively clean that tower with the baffle out. Also, of course, it should be possible to test the vacuum pressure required to close the valve, if I first block the tower base with a glass or acrylic plate. That will allow me to see the diaphragm in action, and I can pull the vacuum with a simple MITYVAC hand pump.

That will have to wait until next week though. We are packing up now to leave town for a week or so. I will leave myself a note, so I don’t forget.

Thanks for the information. No, I just had not thought to try and pull the baffle out the bottom.

Regards,
James

Sun Jul 20, 2008 1:19 pm

Oh,
I also like your work on the throttle body switches. I plan to look into that also when I return.........very likely will place an order.

James

Sun Jul 20, 2008 1:39 pm

Thanks. Enjoy your trip!

Mon Jul 28, 2008 10:28 am

OK tencent,
I am back in Nevada, and today I took the case breather tower off again for testing. I have only the trip to the airport and back on it, say, 25 miles or so.

As planned, I cut a square of acrylic sheet to size, drilled and fitted it to the base of the tower. I then rigged a hand vacuum pump with its own gauge to the tower outlet pipe. I also used a “T” connection to plumb a Snap-On vacuum gauge in the line. The valve operation then was easy enough to see (with the baffle first removed) through the acrylic base plate.

The result surprised me completely. Neither of my gauges is sufficiently sensitive to obtain the actual and precise value that valve closes at, but it is small indeed. With the Mityvac gauge I couldn’t see any movement at all. On the larger snap-on gauge I could detect movement but less than half an inch Hg is all I can be sure of. With the little hand pump it was possible to increase and release the vacuum slightly and watch a positive closing and opening of the valve but the action was too delicate for my set-up to measure. The valve would open and close with no change in the gauges. My guess is that it was closing in the .2 to .25 in/Hg range. This valve is operating at far less vacuum than I imagined.

The implication is that that valve will close as soon as the engine starts and remain so throughout the operating range, except for opening during WOT. Interesting isn’t it?

James

Mon Jul 28, 2008 8:00 pm

Right, it would open at WOT, but also at idle, as there isn't any vacuum in the intake boot with throttle closed.

It would have to be pretty sensitive to work at all. Pretty interesting, yes. I just wish they had made it replaceable without such great expense, or at least had built something more durable.

I have like three towers around here at the moment, and not one functions as designed.

Mon May 04, 2009 4:37 pm

Ok, here is my idle issue.
When I clamped the breather hose, nothing changed.
So I pulled what looked like a blue wire that I think is for the Idle control valve.
Here is what I umplugged:

Just as soon as I unplugged this wire the idle went up to around 1,100 RPM and smoothed out considerably.
Can anyone tell me how this should be remedied?

Mon May 04, 2009 4:44 pm

On second read, this is the wire for the O2 sensor.
If I unplug it and the idle smooths out does this mean that the O2 sensor is bad?

Mon May 04, 2009 4:46 pm

What you pulled is the O2 sensor. The wire is actually a Fat Green one? If it is, then your O2 may be a contributor to your issues. If you never replaced it, it is a 50-60K change item, or if your running poorly. When the engine is in warmup mode, the O2 is not part of the calculation as the engine is in warmup, controlled by the Temp II sensor. When it gets to the proper temp, then the engine uses O2 data (Lambda) to adjust the mixture and timing. The Mixture is adjusted by changing the pulse and duration of the fuel injectors.

Have you looked over the ProTraining Manuals to get an overview of the system? You can follow the setup on there and systematically get everything set up properly. If your O2 is gimp, then change it out first. You can get the less expensive universal kit, just ensure it is a Bosch one.
:

http://www.van-cafe.com/home/van/page_345_756/oxyg...nnect.html

Mon May 04, 2009 4:49 pm

That would also probably attribute my terrible gas mileage huh?
Couldn't hurt to replace.
I'll go ahead and order it.
Thanks.

Mon May 04, 2009 4:55 pm

Just ordered it.
We'll see.

Mon May 04, 2009 4:59 pm

Yes the O2 will pay for itself over a fairly short period of time. If you don't have the Protraining manuals, get them from my public folder:
86 Vanagon Protraining.pdf
Vanagon Protraining Digifant I 86-91.pdf
Vanagon Protraining 86-91 Fuel Systems.pdf

So if you want a better schematic get it from my public folder:
Vanagon Wiring Diagram.pdf

http://homepage.mac.com/WebObjects/FileSharing.woa...mp;lang=en