Pics as requested/promised. These are pics of my original VCV. No adjustment screws I can find. the 'new' one I got from the yard is not nearly as pretty looking. In fact its rusted out on the inside! But it is identical.

Observations:

1.) My original one is defintely broken, the spring is not properly attached to the shaft for a smooth opening of the valve that regulates the amount of air thats allowed in. This looks like a primary mode of death for these things. The attachment of the spring to the shaft is a weak point.

2.) This must bleed at least some vacuum 100% of the time. The seal is metal on metal for the closing of the valve. Theres gotta be some bleed, or at least some is acceptable. Im not sure, this is just an observation.

Conclusions thus far:

-Back to the junkyard(s) to get a VCV thats not rusted out, and doesn't have any visual breakage internally.
- lets see if my local MB guys will let me test a new one with the MityVac and see what it does.

-dd

Attached Thumbnails

   

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'85 300D, 'Lance',250k, ... winter beater (100k on franken-Frybrid 3 Valve Kit)
'82 300D, 'Tex', 228k body / 170k engine ... summer car
'83 300TD Cali Wagon 210k, wife's car

DD,
Good work with the pictures... yes your picture was worth 1K words! I was not even aware the top part would come apart as you show.
Don't forget to ask your exemplary MBz parts people if their new VCV(s) are adjustable!
Regards,

Does anyone know what the orfice part number is that goes in the vacuum hose comming from the pump to the brake booster? It has two nipples on it that break easy after becomming brittle. The hose is like $50.00, I thought you could just buy the orfice but have not found any.

We've all done it..........the plastic piece is not available.........you must purchase the entire line.

SteelBender... take a look at the vacuum pump-TO-brake booster line at this link on our sponsor's WebSite:http://img.eautopartscatalog.com/live/N402074174OES.JPG
This is for a 1985 300SD... Q - What is your car... YR & model and how many miles ?

If you are talking about a "T" like the smaller one that is mid-way on this line, then I I would think seriously about using copper/brass fittings available in the plumbing department of your local hardware store... but before I would try that I would try and get a measure of just how brittle this old plastic line is. IF the plastic line is strong and NOT brittle, you might make repairs but if it's the other orifice tap that is near the right end of this line, then I think there is also a check valve in this fitting!

Also IF you do attempt this, do not restrict the line too much for it is IMPORTANT to have a full flow of vacuum to the brake booster!
Regards

So...more junkyarding today. First, here is what I found from the MB parts guy.

For old style VCV's, PN:1230700046. (its printed on top of the VCV). He said that: They are supposed to bleed a little bit even when closed. The spec is an average 1 mmHg per second. Max bleed per second is 3 mmHg. Based on testing 10 of these things I have to believe this to be true. I now have one from an '85 TD that falls within this spec. I have 3 others that are bad now on my bench. Here is what I have learned from dissecting them:

- the internals are very simple. a simple spring that breaks a 'seal' is all there is.
- they are prone to moisture getting in and rusting the spring and metal prts out, seizing them or other wise.
- the primary failure is going to be the spring failing somehow. the symptom of this is the lack of ability to bleed vacuum off. On my original one the spring would no longer open the valve, no vac bleed ever. On another one I have the spring seizes at the top position, not pulling the valve back one max bleed has occurred.

Here's how to do a comprehensive test for those reading along:
* this is not an MB official thing, this is my inferred procedure.

Take VCV off IP.

1.) Test with MityVac. Disconnect all vac lines. Attach mityvac to top input. With throttle at min, it should bleed at a rate of 1mmHg/S from 10 to 0 or so. Much more than 2 mmHg/S I'd replace it. I think the rate will naturally be slower the lower the vacuum. From 5-0 should be slower than 10-5 etc. This makes intuitive sense to me.
2.) Feel throttle position input mechanism on VCV. Pushing up you should feel the resistance of a spring. If you fee no resistance it's busted. When you go to full throttle and let go of the throttle input lever the spring should push the lever back towards the min throttle position. If it stays at full it's busted.
3.) Mity Vac again. Pump up at min throttle. While vac is going down, move throttle lever slowly up. At some pint it will bleed out the vacuum. Good.
4.) Take off the two screws and remove the side panel of the VCV. Take a peek on the inside. Rust inside is bad. If it is a junkyard find look for one that still had the vac lines connected to it - this keeps moisture out. Look for general signs of mechanical unhappiness. Youll know it if you see it.

If it passes all of these then you have a good one, as far as I can tell.

Optional: When you have it open, clean it of big gunk that may have accumulated, and put some WD40 on the spring for rust prevention and lubrication. I also sprayed some WD40 on the outside moving parts. Careful not to get it near the valve. This all made my junkyard one a little smoother and good as new, far as i could tell.

If helpful I can post some pics. I plan to put all of this in a document at some point when I hopefully get my tranny working. Hopefully I am now on to the next phase of tranny fixing - I have replaced all of the vac components, so now its time to adjust the cable and modulator. Wouldn't it be nice if after all this the tranny actaully shifts correctly?

-dd

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'85 300D, 'Lance',250k, ... winter beater (100k on franken-Frybrid 3 Valve Kit)
'82 300D, 'Tex', 228k body / 170k engine ... summer car
'83 300TD Cali Wagon 210k, wife's car

Brian, that one does not look like mine, my Car is a 1985 300d Turbo, it has 317,000 miles on it

Here's yours:

http://catalog.eautopartscatalog.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=1XL0VHEI01YN00RRFU&year=1985&make=MB&model=300-DT-001&category=All&part=Booster+Vacuum+Hose&appChassis=_any

DD - Excellent report above in POST #156 under the title:
"Everything you ever wanted to know about the VCV and were afraid to ask"...
I must admit the student has outdone the teacher IF I can be so brazen to think of myself as a teacher about VCV(s) for a brief moment. Also you made an excellent summary about testing used VCV(s).

In going forward, I hope you end up with an adjustable VCV. Keep up the good work and reporting back to this THREAD for your VCV subject is an excellent adjunct to my original premise regarding criticallity of getting the correct vacuum signal being sent to the tranny's modulator BEFORE you start adjusting the modulator.
Regards,

How do you get to this pink pod? Do you have to pull the dashboard out?

My '87 runs great but slams into gear. Shift points are correct though.

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'87 300D 183K
'06 E320 CDI 10K

Is inconsistent shifting a sign of a failing vacuum pump? Sometimes my 300D will shift with a clunk through most of the gears, other times it'll be a hard 1-2 shift, then a soft 2-3. It can differ from stop light to stop light

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1985 CA 300D Turbo , 213K mi

You may remember this thread:

From hard shifts to flaring

Brian in particlualr helped me get the vac on my pump down to 8" at idle. The car is shifting great ever since. Brian did note that when I performed the tests he prescribed that I have a:

"vacuum leak at the modulator on the side of the transmission. This is usually caused by leaks in the rubber cap. But, 23 seconds is not a catastrophic leak. I'd like you to fix it because it affects how we do the remaining adjustments."

With Brian's help we solved the then pressing problem without dealing with the diagnosed leaky cap.

While changing my brake fluid yesterday, I noticed that the cover on my modulator valve located on the transmission is torn.

If I seal up the tear or replace the torn rubber, what difference should I expect in my now flawless feeling shifting?

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Pictures of the MB: http://s230.photobucket.com/albums/ee41/EricandRobyn/1981%20Mercedes/

1981 300 SD with a Goldenrod water block and Injetor line heaters. EGR is missing

1999 F-350 with HP X-over, Dahl 100 Fuel Filter, Coolant by-pass filter, CCV mod, Tymar intake.

Both on single tank WVO blend

Well, the vacuum to the trans will certainly climb.

What the result will be is unknown. Worst case is softer shifts with some flaring.........depending on the condition of the trans........requiring another VCV adjustment..........

... I'm inclined to say that you should always repair known vacuum leaks in the Engine/Tranny Vacuum Control System which includes these components[listed in the order that make the most sense to me... starting at the vacuum source]:
(1) Restricted orifices at the "Ts" in the vacuum pump-TO-brake booster line,
(2) Switchover Valves controlling vacuum at idle and max throttle by a mechanical connection to the throttle linkages,
(3) More restricted orifices,
(4) dashpot/surge chamber with it's likely restrictions,
(5) Vacuum Control Valve with its mechanical connection to the throttle...that performs an increasing/controlled bleed off of the vacuum as you increase the throttle, and
(6) transmission modulating valve.
[ And don't forget that on later models (especially the CA cars up thru 1985 and maybe later) you can have an additional 4 or 5 components that are designed/intended to perform specialized "tweaking" functions like soften the sifting until the engine/tranny warms up, special turbo infaces etc.]
Thanks for enduring this oversimplified recap of components!!

So YES, repair these known vacuum leaks at the tranny's modulator but realize that this might just affect how the transmission shifts and necessitate re-tweaking things IF you are a perfectionist and want your transmission to shift properly and thus last longer.
Regards,

so tonight will be the moment of truth...I will reinstall my VCV and test the vac system - which has to work - I have tested, removed and replaced almost every component.

Here are the steps I am going to take:

1.) Reinstall VCV, check system with MityVac, car off. Want to see bleed equal to that of my VCV bench tests
2.) Turn car on, T in vac gauge at the transmission vac line.
3.) Look for 15mgHg at idle, dminishing smoothly to zero at full throttle.
4.) Ideally, if I was able to, here is where I'd adjust the range of the vacuum signal with my adjustable VCV, if I had one
5.) Adjust transmission shift cable to proper default setting. I understand this to be slight amount of tension at min throttle (Brotherton article).
6.) Ideally I'd check the modulator, but I have no idea what the default setting is, so I'll just have to...
7.) Drive and hope. Make adjustments based on shift timing/quality.
8.) In all likelihood, report back here with new transmission problems.

Any comments, or anything crucial I'm missing?

As I have alluded to before, if I get this all sorted out I'll do a write up with pictures that sums this thread up...I get this vacuum thing now. It's not that bad once you get it - but terrifying initially if you don't.

-dd

__________________
-------------------------------
'85 300D, 'Lance',250k, ... winter beater (100k on franken-Frybrid 3 Valve Kit)
'82 300D, 'Tex', 228k body / 170k engine ... summer car
'83 300TD Cali Wagon 210k, wife's car