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Tue May 22, 2012 4:31 am

I have been messing with my 82 for over 4 years now trying to figure out why it would start fine, idle fine for about 20-30 seconds, then drop and idle poorly until fully warmed up after driving a bit.

I searched in detail for a vacuum leak, performed multiple tune ups, checked valves, etc...nothing worked.

Then last night as i sat looking at the engine shaking around with the usual poor idle and hearing the hissing sound I have been hearing since I bought the thing I decided to check out the PCV valve (or whatever the actual name VW uses) as I never checked that thing out..

Well I happened to pull it out of the tower while the engine was running and nothing changed except for the blow by coming from the hole in the top of the block where the PCV sits. Then I plugged the hose that connects the PCV valve to the S-Boot , and the idle immediately kicked up, steadied itself out, and my engine vacuum gauge that I have mounted on my dash went up 3 inches from a crappy jumpy 12-10 to a steady 15.

My thought is that that PCV is completely faulty and I plan on leaving the setup as it is for a bit, check my gas mileage with a new full tank, and monitor my head temps and see if anything negative occurs.

My feeling is that there is no issue running the engine in this manner as it would be no different than the way engines used to be operated before the advent of emission control systems where there was simply a hole in the valve cover which was vented directly to the atmosphere or back into the air cleaner.

The system VW designed, I believe, is faulty in that it returns blowby to the system post AFM and any issue in that link will fubar the air/fuel mixture.

What is the consensus here? Does this make sense?

Regards

Tue May 22, 2012 5:05 am

You need to get rid of your blowby somehow. Leave the hose off and let it dump on top of the engine and you will have an oily mess in short order. The problem you are seeing is probably why VW added a restrictor to the vent hose on later Vanagon engines, to take out the pulsations, so adding a restrictor might be a good idea, for some reason I remember hearing that the original one is 5.5mm in diameter.

One solution would be to plumb the blowby into the air cleaner box so that it enters the air stream before the AFM. This way it will still pass through the engine, but the pulsations will not affect the AFM much at all.

Don't know if you are old enough to remember pre PCV roads or not. There used to be greasy strips down the middle of each lane, that were pure death on motorcyclists and made the roads snot slick in the rain for motorists as well.

Tue May 22, 2012 5:12 am

Wildthings wrote: You need to get rid of your blowby somehow. Leave the hose off and let it dump on top of the engine and you will have an oily mess in short order. The problem you are seeing is probably why VW added a restrictor to the vent hose on later Vanagon engines, to take out the pulsations, so adding a restrictor might be a good idea, for some reason I remember hearing that the original one is 5.5mm in diameter.

One solution would be to plumb the blowby into the air cleaner box so that it enters the air stream before the AFM. This way it will still pass through the engine, but the pulsations will not affect the AFM much at all.

Don't know if you are old enough to remember pre PCV roads or not. There used to be greasy strips down the middle of each lane, that were pure death on motorcyclist and made the roads snot slick in the rain for motorist as well.

i was also thinking of putting some type of filter in place - like in the old days if you recall those plastic inserts with the filter inside that plugged into the valve cover. Exact same concept. Regardless, it will be a better solution than the existing one as the system will be tightened up with regards to possible vacuum leaks.

Tue May 22, 2012 6:00 am

I had done a similar experiement as you... even drove a short bit with that hose disconnected and the tower having a length of tubing to a catch can to confirm it ran well. Then pondered how to close the system and still get the same effect.

I added said restrictor -- just got a white plastic plug from the plumbing department at Ace and drill a 5.5mm (7/32") hole in it. It was a snug fit in the hose at the end towards the tower. That got my idle settled down & nice with no hesistation at tip-in.

Tue May 22, 2012 6:20 am

Ahwahnee wrote: I had done a similar experiement as you... even drove a short bit with that hose disconnected and the tower having a length of tubing to a catch can to confirm it ran well. Then pondered how to close the system and still get the same effect.

I added said restrictor -- just got a white plastic plug from the plumbing department at Ace and drill a 5.5mm (7/32") hole in it. It was a snug fit in the hose at the end towards the tower. That got my idle settled down & nice with no hesistation at tip-in.

You removed the PCV valve from the system entirely correct? So now all you have is the hose from the S-Boot with a restrictor between there and the block correct?

Tue May 22, 2012 6:32 am

No, the hose is now reconnected as before but inside it is the 5.5mm restriction. This is on an 84 WBX so I cannot say if your setup is identical.

The PCV / breather tower is now useless, the diaphragm (like most I suppose) has disintegrated.

The restriction is inside the hose here:

Oops, inside that big hose of course, not the little vacuum line the arrow also points towards.

Tue May 22, 2012 7:55 am

I don't know if the WBX is different from the air cooled models. My goal here is to completely plug the hose from PCV into the s-boot, therefore completely elimination the possibility of a vacuum leak.

I think wildthings nailed it when he suggested to plumb the blowby into the airbox and be reburned. However I wonder if the air filter would be prematurely clogged then.

May be that the only way to accomplish what I want is to use the old school valve cover breather with the foam like insert that vents directly to the atmosphere.

Tue May 22, 2012 8:14 am

With the case breather going into the air filter, I would think about an oil catch can between the two? Just a suggestion.

Tue May 22, 2012 8:39 am

Many older rigs used some form of PCV filter in the air cleaner if they dumped the gases into the air stream before the filter. Don't think this would be necessary if the gases were dumped in after the filter. Every rig is a bit different though so you won't know until you test it.

Tue May 22, 2012 9:59 am

Wildthings wrote: Many older rigs used some form of PCV filter in the air cleaner if they dumped the gases into the air stream before the filter. Don't think this would be necessary if the gases were dumped in after the filter. Every rig is a bit different though so you won't know until you test it.

yes that is correct on the inside of the old air cleaner units there was always a filter that clipped on to the tube coming from the valve cover if that was how it was setup.

Tue May 22, 2012 11:50 am

In case you decide to try the restriction (and for the benefit of future searchers) this is the plug I used:

...with a 7/32 hole drilled thru.

The threaded end went into the snout on the tower and the hose fit snugly over the hex head of the plug.

The Ace label...

Even if you choose to dump that 'air' so it gets metered I think the restriction will temper the pulsing nature of the wide open tube and yield a better result (idle).

Tue May 22, 2012 1:15 pm

The PCV was an air leak I found when I pressurized the system. Temporarily you could just plug the air relief hole on the valve but make sure you put a new o-ring on it so i seals in the case. I cut mine open and repaired the diaphragm :

It is still holding. There was a lengthy discussion about it on the bay forum and it seemed the general consensus was that it was needed for longevity even though you can just attach a hose directly from the the breather port to the air intake elbow.

Tue May 22, 2012 1:23 pm

Here is the link for the bay discussion which also has some picts of a a similar valve taken apart.
http://www.thesamba.com/vw/forum/viewtopic.php?t=2...highlight=

Tue May 22, 2012 2:01 pm

Yeah, I saw this on ebaY and wondered if it could be hacked to work as a replacement diaphragm:

http://www.ebay.com/itm/Gulp-Valve-Diaphragm-MGB-S...mp;vxp=mtr

Tue May 22, 2012 2:31 pm

I saw that a few years back. It might work....it looks like it can be trimmed if needed, but I am not sure if that would effect how the valve works. I think it is mainly the spring that controls when it closes due to vacuum so maybe as long as the diaphragm is cut to the right size it would not matter. I have another to repair so maybe I will try it.

Tue May 22, 2012 4:28 pm

Ahwahnee wrote: Yeah, I saw this on ebaY and wondered if it could be hacked to work as a replacement diaphragm:

http://www.ebay.com/itm/Gulp-Valve-Diaphragm-MGB-S...mp;vxp=mtr

For less than 5 bucks delivered it would be worth buying several and doing some experimenting.

Tue May 22, 2012 10:41 pm

Cool topic. My van does something similar so I can never warm it up. I just start and drive away. If I wanted to start it up and leave it running it has a 50/50 chance it will stay running. If I drive it a block, stop then it will idle smooth and warm up. Sounds similar to what is going on here.