Autostick control valve disassembly & inspection

[sb001]

Lately my 69 autostick beetle has been having a bit of trouble with low idle at stops in gear (once the engine has warmed up.) I have seen a few other postings where other autostick owners have had similar issues.
It was suggested that perhaps my autostick control valve had a small vacuum leak or one of the valves (there are 3 inside the assembly) may be sticking. This could conceivably cause the control valve to constantly be pulling vacuum away from the throttle body thinking it has to "recharge" the vacuum in the autostick system, thereby causing low idle esp. in gear.

So.. with the help of an exploded view diagram of the control valve from the Bentley autostick section:

I decided to undertake the task of disassembling, inspecting, and reassembling the control valve. I have not come across a procedural thread for this so I decided to document it here.
_________________
I'm the humblest guy on this board.

1969 autostick sedan, family owned since new
1600 SP engine
Solex 30 PICT 3 carburetor
Bosch 113905205AE autostick distributor

[sb001]

First off, for those unfamiliar with the autostick control valve, it is a housing mounted to the upper left of the engine in the engine bay, if looking at the engine from the back. Here is what it looks like installed:

The horizontal arrow points to the vacuum hose between the control valve and the intake manifold. The hose directly behind this arrow is connected to the vacuum tank under the left rear fender (or right rear I think in a ghia.)
The vertical arrow points to the smaller vacuum hose going from the control valve over to the extra port on an autostick carburetor. This monitors the vacuum signal at the throttle plate and keeps the autostick vacuum charged, which allows the control valve to keep a constant vacuum signal to the engine.

The third large hose connected to the control valve goes through the firewall to the clutch servo:

The control valve blocks the vacuum tank from from sending a signal through to the vacuum-controlled clutch servo diaphragm mounted to the top of the transmission until the clutch servo needs it.

Here is a diagram showing the clutch servo mounted to the transmission:

When the driver shifts, contacts in the base of the shifter rub together and complete a circuit sending an electrical signal to the solenoid on the rear of the control valve. This activates a valve inside the CV housing that allows some vacuum from the vacuum tank to go through to the clutch servo canister activating the clutch and allowing the transmission to shift.
_________________
I'm the humblest guy on this board.

1969 autostick sedan, family owned since new
1600 SP engine
Solex 30 PICT 3 carburetor
Bosch 113905205AE autostick distributor

[sb001]

OK, here is a picture of the control valve uninstalled from the engine bay. It is simply held in place to the sheet metal on the left of the engine bay via 3 10mm mounting bolts.

You can see the solenoid (the large cylindrical object) attached to the rear of the housing with the two electrical wire connections (one for power from the ignition coil, and the other from the contacts in the gear shifter.)

Let's get started...
_________________
I'm the humblest guy on this board.

1969 autostick sedan, family owned since new
1600 SP engine
Solex 30 PICT 3 carburetor
Bosch 113905205AE autostick distributor

[sb001]

First I removed the air filter canister from the front of the control valve
housing:

It simply screw in to the front of the CV and can be removed with a 17mm wrench.

It can be soaked in kerosene or gasoline to clean it out.
_________________
I'm the humblest guy on this board.

1969 autostick sedan, family owned since new
1600 SP engine
Solex 30 PICT 3 carburetor
Bosch 113905205AE autostick distributor

[sb001]

Next, I began disassembly of the main valve shaft which the solenoid is mounted to. First I removed the 4 flathead screws holding the solenoid to the control valve housing:

With the solenoid removed, you will see a largish spring:

This is the solenoid spring that pushes the main valve when the solenoid is activated.
Removing this spring you can now see the seat that it pushes against, with the actual valve underneath:

Once the seat is removed you can see the 24mm sealing ring and the actual main valve beneath:

Removing these will reveal the main valve spring underneath which can now also be removed:

_________________
I'm the humblest guy on this board.

1969 autostick sedan, family owned since new
1600 SP engine
Solex 30 PICT 3 carburetor
Bosch 113905205AE autostick distributor

[sb001]

Next I tackled the reducing valve shaft. This is the top of the shaft that holds the reduction screw that controls how fast the clutch actuates:

First I removed the screw, then the concave washer that helps hold the shaft cover in place (this has to be pried out with a small screwdriver.) Once these are removed you can then remove the cover and see inside:

What you are seeing here is the retainer cap on top of the spring inside the shaft. If you remove this cap, and the spring underneath, and then the bottom spring retainer cap, you will see the reduction valve underneath:

Removing this valve will reveal the top of the diaphragm spacer in the bottom of the control valve housing:

_________________
I'm the humblest guy on this board.

1969 autostick sedan, family owned since new
1600 SP engine
Solex 30 PICT 3 carburetor
Bosch 113905205AE autostick distributor

[sb001]

Next comes the tricky part--removing the main diaphragm from the control valve housing. Luckily I had a spare control valve (with a bad solenoid) that allowed me to practice on it first, and it's a real good thing I did. (I'll get to why in a second.)

Turning the control valve upside down reveals the diaphragm cover on the bottom:

I removed the four flathead screws that hold the cover on and took off the cover. The main diaphragm is underneath:

Now here is the tricky part. I thought that I could just pull the diaphragm out from its housing, but try as I might I just could not get it to come out. I finally pulled hard enough that I ripped the rubber at the other end of the diaphragm rod! Before I yanked on the diaphragm:

After I yanked on it (arrow points to part I ripped off):

Luckily I did this on the SPARE control valve I had, so I did not ruin the one from my car!
I finally realized that the rubber on the other end of the diaphragm rod is actually a rubber SEAL, that SEALS the diaphragm rod to the dished support that it sits in.
If you bend back the main diaphragm as I am doing in the picture above, you can see a small hole in the support that you can stick a small screwdriver or tool in and pull the support out, WITH the diaphragm. Once out, you can see how the diaphragm and its support are basically all one piece, with the hole used to leverage the assembly out:

And the seal that holds the diaphragm shaft to the support:

_________________
I'm the humblest guy on this board.

1969 autostick sedan, family owned since new
1600 SP engine
Solex 30 PICT 3 carburetor
Bosch 113905205AE autostick distributor

[sb001]

Removing the diaphragm (and the spacer mentioned earlier) granted me access to the two screws that hold the diaphragm housing to the main valve housing:

Removing these two screws proved to be a pain, they were in VERY tight and I actually had to use a ratchet with a flathead bit on the end of it to get them loose. Once loose I found a bunch of crud on the screws:

Once the housings were apart I could then get to the check valve and spring:

I removed these and inspected them for grime and stickiness which it did appear they had a bit of. So I cleaned them with a rag, and then inspected the two housings a bit more closely. They both had this residue on them as well:

So I soaked them both in carb cleaner and will scrub that residue off once they have soaked for a good while.
_________________
I'm the humblest guy on this board.

1969 autostick sedan, family owned since new
1600 SP engine
Solex 30 PICT 3 carburetor
Bosch 113905205AE autostick distributor

[sb001]

I hope this thread helps any autostick owner who might wish to inspect the control valve for issues and/ or clean it thoroughly. Even if you are not experiencing any problems I would still recommend this procedure as it will allow you to thoroughly clean the control valve housing body and internal parts -- after 40+ years of probably never having been taken apart it may be worth the time and effort. It is not a particularly difficult task, just be careful and take your time ESPECIALLY with the diaphragm removal as that is easy to tear and replacement/rebuild kits are not available.

Reassembly is simply a reversal of the procedure outlined here. Once cleaned and back together, your control valve should be good to go for a good long while.

I plan on posting a followup here once I have mine back together and reinstalled to see if it cures the low idle issue I have been having.
_________________
I'm the humblest guy on this board.

1969 autostick sedan, family owned since new
1600 SP engine
Solex 30 PICT 3 carburetor
Bosch 113905205AE autostick distributor

[67rustavenger]

SB001,
This is a very well documented write up on the disassembly of an autostick control valve. Nicely done for sure!
Can you take it a bit further and document the cleaning and re-hydration of the rubber components and the reassembly of the control valve?
I think others that have the autostick trans in their cars would really appreciate a complete write up of it from start to finish.
Please understand that I am not being critical here.
I am a little curious as to why you posted this write up in the general topic forum, rather than the 68 up forum. It just seems like you would get this to be a possible sticky in that forum.
This is really nice work that you have done in this post.
Thanks for this fine contribution to the ACVW community. Someone will surely benefit from your efforts.
Have a great Forth of July Weekend.
_________________
I have learned over the years.
Cheap parts are gonna disappoint you.
Buy Once, Cry Once!

There's never enough time to do it right the first time. But there's always enough time to do it thrice.
GFY's Xevin and VW_Jimbo!

[raygreenwood]

[67rustavenger]

raygreenwood,
I would not even think to argue with you regarding re-hydrating rubber parts. But since you seem to have an extensive chemical background. How would you treat rubber components that are 40 years old and are NLA to keep them pliable? Just a curious question that most likely needs an answer for a very knowledgeable chemist/engineer involved in the chemical industry.
Have a safe Forth of July weekend.

[sb001]

[johnnypan]

[SBD]

I used to use a product called Lexol Leather Conditioner on my motorcycle leathers. You would use a very small amount and work it into the leather with your hands/fingers. Worked amazingly well on leather and left your hands unbelievably soft & smooth after working with it. A quart bottle would probably last most people a lifetime. Might work on rubber.
_________________
"Just $99 down and $64 a month for 36 months buys you a brand new Volkswagen Beetle!"

[volkenstein]

SB,
Check out this post on VWAR OLD forum :
http://vwar.org/old_forum/index.php?topic=376.0

Did much the same years ago. Some tips in that post for you re cleaning small drillings in the body etc. FYI.


HTH
Volkenstein
_________________
71 RHD AS Super - "Klaus"...
Wisdom of youth, energy of old age...

[olspeed]

Most of those O- rings are going to be standard sizes so go visit your friendly CAT or John Deere dealer and see if they can match them up for you as both companies use metric O-rings and square cut rings and should have an ample supply, also I would be willing to bet that the OEM VW rings are nothing special so a Buna ring will work just fine.
_________________
66- Ghia
76-Beetle

[itskyle]

Hey,

I really appreciate all of this information that is posted. I have the Bentley, but it is really neat seeing this in color.

I have a couple of things:

1. Rubber-preserving-I always go to belt dressing, but maybe cosmolene or some other substance with the same consistency, since these rubber parts need to pump air.

2. The housing itself, is there any benefit in coating it with something so even if it cracks, the coating prevents air from leaking?

3. Solenoids for this are NLA, I am certain. Any possibility of component level repair on the solenoid? That may be more of an EE question than anything else.

Kyle
_________________
--
69 or 72 Autostick Bug current
66 Bug (We both miss it)
74 SuperBeetle Auto Stick (I miss that car)
73 SquareBack, Straight Stick (Wife misses this one.)

[volkenstein]

Itskyle,
No chance...if it dies (solenoid) get a second hand one. I attempted to perform surgery on one of these once....and without specialised equipment to take it apart - you have no hope of ever getting it back together.

Probably a good point to seal the outer solenoid body to the inner "cap" (that has the electrical connections) with silicone seal. The rubber sealing ring on the above attempt had perished outrageously.

Volkenstein
_________________
71 RHD AS Super - "Klaus"...
Wisdom of youth, energy of old age...

[itskyle]

Actually,

I had one more, and that is whether or not a 3D printer would be able to remanufacture or duplicate these kind of rare oddball NLA parts, or, better still, improve upon the original design?

Kyle
_________________
--
69 or 72 Autostick Bug current
66 Bug (We both miss it)
74 SuperBeetle Auto Stick (I miss that car)
73 SquareBack, Straight Stick (Wife misses this one.)