Your Control Valve - Unplugged!

[volkenstein]

Here we are after fitting the waisted rubber mounts and bracket...
Looks lurvly don't it...but does it work?



NO. If I fitted this as it is now, I reckon it would thump.

I'll explain. On my other two (on Klaus and my spare) when I push the diaphragm down and place my finger over the brass vacuum fitting, the diaphragm maintains position. Not so on this one.

I could hear air being pumped/sucked. The diaphragm piece itself is OK.
Maybe I screwed up with the Rustbullet? I removed it all from the diaphragm cover (the underside) and while I was at it I smeared permatex on the underside of the steel doohickey and on the underside of the rubber washer. Re-assembled and still not holding vacuum.

For my next trick, when I dissassembled it again, the Permatex ring on the underside of the steel doohickey was untouched!!

I made up two paper gaskets .4mm thick and placed them above and below the large section of the diaphragm as the Permatex under the rubber washer was well and truly spread. Put it all back together and this time it was much better, but I still have a leak there.

It got too cold and I need to find some thicker gasket material.

What happened?? I think my cleaning of all the corrosion has actually contributed to the problem. The rubber washer and the larger of the two diaphragm rubbers have been well and truly crushed with age. They don't leak by themselves but need to be properly spaced to seal.

I'll post back on what I finally end up with as a solution......

Is there a moral?? Well, never ever buy a corroded one if you need a spare :lol:



Enjoy
Volkenstein

[68AutoBug]

I didn't think that would end up looking like that Sean...
Very Good...
My Control valve is mostly Green....
I'm wondering now that If I have to have the engine lid open at the top in the summer... what effect will rain have on the little breather on the control valve....
Should I use a right angle fitting so it sits upright....
or have it sitting up under the top of the engine bay....??

Have You ever tried to drive with the small vacuum hose off..
It takes ages for the clutch to release....

Lee Noonan    http://community.webshots.com/user.vw68autobug

[volkenstein]

Lee,
     Provided all the hoses are hooked up, the rain won't affect the CV that much. What I would do is use RTV sealer around where your adjuster screw is, on the cap as water can seep down until it hit's the O-ring and cause "calcification". The diaphragm sit's upside down in the "normal" position so water won't leach into it.
The brass spigot has a tiny, tiny "jet" in it. Any rubbish could easily block it.

After all my mucking around and comparing various schematics, leaving the hose off the brass spigot will delay clutch engagement by almost a century! When the modulator isn't functioning (via the diaphragm) the only place for air to enter the CV/servo is via that teensy little port near the modulator check valve (I photo'd it in the first "page" of this post).

When you accelerate, vacuum from the carb venturi causes the diaphragm to push the modulator check valve off it's seat, and filtered air is drawn in quickly allowing the servo to release the clutch.
The adjuster screw for your shift engagement speed regulates how far and fast the check valve is raised and closed.

Which I guess is another way of saying....even a restricted "T" piece from manifold vacuum is not as VW intended :lol:  But the proper fix may well be impossible if you don't have a place to fit a venturi vacuum fitting on your carb of choice.......

That's my random thoughts anyway.....


Volkenstein

[volkenstein]

All,
   So I pulled it apart to check what had happened with the twin paper gaskets.....



The bottom right gasket shows no sign of being compressed by the steel ice cream cone. The bottom rubber seal got a bit more compressed and look where the cap isn't contacting the body.....


Volkenstein

[volkenstein]

All,
   So I ditched the two paper gaskets and found some spare rubber material I used to make a transmission gasket. It was 1.3mm thick.
So I cut a piece 71mm in outside diameter and 61 internal diameter.
This I placed on top of the large diaphragm rubber and didn't use the two paper gaskets.....

This time it was worse :cry: . The diaphragm steel cap started to bow as I tightened the little cap screws so that was the end of that.

After a  bit more thought and measuring I seriously believe I'll be making a new thinner bottom rubber piece (bringing the steel support closer to it's upper seating lip), using a paper gasket on top of the diaphragm rubber and running RTV around the cap sealing lip and around the outside edge of the large diaphragm rubber......


Volkenstein

[volkenstein]

All,
   Took it apart again, and measured various depths and stuff. By my calculations, the ice cream cone doohickey seals on the bottom seal, and the top diaphragm rubber is held against upper section's lip by the cover plate. Self centering if you like.

So I threw away all my gaskets and placed the seal/cone/diaphragm assembly in the housing and ran a thickish bead of RTV around the circumference if the diaphragm rubber (which I noticed, has clearance between it and the alloy housing...something that definitely isn't there on my other spare...so maybe the rubber shrunk back?).
Carefully put the cover on and waited about 1 hour then tested with a Mityvac pump. Much better. the diaphragm moves with 5 in/Hg vacuum and moves slowly back to it's resting position.

I'll check the RTV seal as I may have not made it thick enough, and I'll see if I can narrow down exactly where it's allowing air in.


Volkenstein

[volkenstein]

All,
   I took the cap off and the RTV had completely sealed the diaphragm/cap/support....spent the next hour picking it all out.

I had a look at the diaphgrams and there are no pin holes, so my next area of sealing will be around the plate that the adjusting screw nut is on.

I think I can put my ciggie habit to good use by blowing smoke into the brass spigot (when I've reassembled it), sealing it off and then pressing down....maybe I'll be able to detect where it's leaking....maybe not.

Curil K2 is going to be the weapon of choice for the upper plate, RTV around the diaphragm again.....


Volkenstein

[68AutoBug]

I didn't really believe that you would ever get all those bits back together the correct way Sean....
the small vacuum hose came off My carby one day as I pulled onto the highway....
I soon pulled back off as it took ages for the clutch to engage....
and naturally, every time I touched the gearlever...
it took longer....

Its really unbelieveable that these things have lasted so long.....

cheers

Lee --  68Autobug --

http://community.webshots.com/user/vw68autobug

[volkenstein]

Lee,
     Absolutely, even this one as cruddy as it was still had a working solenoid, and the internals were in fair shape.

For a 37 year old weather exposed thing, it's in remarkably good shape internally. The only machanical wear is on the check valve face that the solenoid plunger hits and the reducing unit check valve where the plastic spacer pokes into it. Nothing I can do about the former, but a little re-adjustment of the diaphragm screw takes care of the latter.

I reckon I've been a contributor to the current problem by taking it completely apart and disturbing things!  :lol:

There's a post with schematics by a UK guy with a 356? that explains very clearly what happens with your vacuum and the tiny compensator port. I'll be taking some vac measurements for sure off Klaus when I'm able.

Regards
Sean

[68AutoBug]

I wonder if thats the guy with a replica 356 in the UK... He can't drive a manual, because of a medical injury, so He had a company install the Autostick into the car with a brand new engine....
The company installed a dual ATF/engine oil pump, without changing the oil seals.... and the ATF ended up in the engine.... car didn't go very far...
The New engine wouldn't like running on ATF either...

From what I've read, the maximum oil pressure from the engine is 28 PSI
and the maximum pressure for the ATF pump is 52.6 PSI...

From what I've read so far Sean, You have done more measurements etc than anyone.. anywhere... as for most people the Autostick components are a bit of a mystery....

cheers

Lee Noonan  -- 68AutoBug --

http://community.webshots.com/user/vw68autobug

[volkenstein]

Lee,
     That's the guy, didn't realise he'd had an oil flood :shock: .

So on to tonights effort.

Got the Curil and sealed the diaphragm with that and put some on the reducer adjusting screw and nut while I was at it. More RTV around the diaphragm and button it all back up again.

A slight improvement, it returns to "rest" slower than before. Not much however. Reacts faster to the Mityvac vacuum as well, again not a great amount.....

Next time, it'll be the large rubber washer to body as well as re-doing all the rest.


Volkenstein

[volkenstein]

So,
   After a month overseas getting a drinking problem, I've returned and dried out enough to hook in again!

Pulled it apart yet again and a fun hour it was picking the RTV out of every nook and cranny. The cover/diaphragm/support is fully sealed by the RTV so time to coat other things.

This time I did around the bottom rubber washer and put some on the underside of the large diaphragm, where the aluminium shaft is as well as sealing the two body joining screws.

This time, it reacts instantly to applied vacuum but still manages to return to rest. I've only got two places left and that's around the small diaphragm rubber. I think it's time I also ditched that bottom rubber washer as I think it has now retained the "crush" from the steel diaphragm support and probably is not sealing as good as it should.


Until later on
Volkenstein