Glorious Orifice (Vacuum ), sensational shift, no flare
 

I found one of these in my top tool box tray after I kicked it over in he driveway behind my car. I had been asking at all the auto stores for one of these and was going to try the dealer next . Needless to say, finding it renewed my faith after picking up about a hundred screws, bolts, and nails accumulated over the last few years. ;).

The piece i am talking about is a tiny vacuum coupler (2 male ends) called an "orifice" that you join 2 vacuum lines/Ts/etc with. The key feature is that one hole is smaller (needle point size) than the other so it reduces the volume of vacuum out the small pin hole end . That this piece is important has been mentioned several places but I never knew exactly what its effects were. Except I did read turning it the wrong way ruined the tranny on someones car and I am still curious about that. I went to an Indy and tried to get an orifice. The diesel mechanic did not know what I was talking of and was quite sure the only thing that affected vacuum at the tranny was the VCV and it had an adjustment screw. Lucky I never trust anyone except people on the internet :) .

Nuf Rambling fool. :mad: ! Ok,, here is what the black orifice I found in my tool box tray did for my 1981 300D. I named it "Blacky" :D And mind you this orifice may not even be the right size (a tad small if anything) as they come in many sizes. I can post a color coded chart from service manual if someone wants. First, my problem (posted several places :) ) was flaring in all shifts when I had *any* foot on the pedal whatsoever -- a real pain when you pull out into traffic. Also , the kickdown switch did not work at all but I had dismissed this as a separate issue. I got the car with these problem and varuum lines wired all wrong and crossed. Someone put a new engine in and never got the vacuum right. I guess they did not have internet access. One was put on the metal dashpot thingy on Injection Pump that looks like it wants something hooked up to it (but does not i figure) instead of the vent on the VCV valve. Swithching that made the car much more peppy.

So, first was to fix vacuum wiring and eliminate any excess variables by following the diagram and ditching the black box 3/2 valve and tightening up vacuum leaks. I did this and this made flares a little better (could give it a bit more foot ) but still it flared under most conditions.

Enter Blacky the vacuum orifice between the vacuum source and green VCV dashpot T (one end to VCV, one end to tranny). Great scott, Blacky is like Tranny's brain and now the car can run like the Black Stallion.. When I put my foot on it, not only does Tranny not flare , it stays down a little while longer giving extra acceleration. Like it knows I want to go faster :) It accelarated up a big hill to 30 mph that it usually decelerates up because it stayed down in 2nd gear. No one told me it was supposed to do this. I have not had an automatic in about 3 years. Amazing how It shifts much more consistent with how I would if I were doing it . Also, if I am in no hurry and taking it easy, IT shifts earlier keeping my ride smooth as can be and mpg as good as can be -- into 3rd at about 17 or 20 and 4th at 27 - 30 like it used to but with no flare.

And the kickdown switch works now! It was bone dead before. And I think my climate control temp dial is more responsive.

Other stuff may work better too. I bet if this fixes my cold starting problem and grinding starter :)

Hope all your car days go smooth.

:) Don't you just love it when things like this work?! Excellent. Congratulations.

Of course, if you're like me, the next thing you'll find is a screw (from the kicked over tool box) in one of your tires. I came up one screw short (on the car, not me) when putting the splash pan back under the 190D last week. Next day I find the Eurovan with a flat in the driveway...yepper, must've kicked that screw out into the driveway so it could get planted right smack in the center of that tire (captive washer held pointed it up at just the right angle). At least I found the sucker, and now it's back in the Benz.... !

Many folks don't realize the importance of that small orifice to allow the VCV to do the proper modulation for the transmission.

With just a vacuum gauge and a bit of patience, many of the problems caused by excessive flaring or hard shifts can be eliminated.

Your success proves that a checkup of the system and carefully returning it to specification will provide significantly improved driveability.

Everyone with shifting problems should note this success and take heed.

I was "apprenticed" for one day by the top guy of Mercedes transmissions on the West Coast. I recall he said that there are at least 4 types of these little controlled vacuum splices thingies, black, yellow, tan or brown and green. Either the tan or green one is a solution for early shifts. Adjusting the controlled leak at the rear of the IP is also key to setting up a transmission to shift where it should. He said he was certain that more than a few shops told customers they needed a transmission rebuild when all they needed was to set up the vacuum systems properly.
The first thing he does in checking a transmission problem is drill out the manifold connection, the one that has a small opening (one has a large hole the other a small one). If any dust accumulates in that then the source vacuum deteriorates and all efforts are in vain.
Then he blows air thru this Blackie splice (or green or tan whichever is on the car) to clear it open, then he plugs the lines going to the CLS to remove it from possible interaction (leaking CLS can affect vacuum overall) then he tees in a vacuum gauge to the transmission line. The rest is experience, how far the vacuum needle swings when the accelerator is advanced and let go is what you want to look for. I still have the marks on my vacuum gauge where he specified.
If that doesn't work then you attach hydraulic pressure gauges to the transmission and start taking readings or bench test it.

Pictures
 

I have a 300D and I'm trying to get a hold of one of these, but I'm not sure which ones I'm looking for. You say this is different from the green dashpot? My diagram says I need 2 orifices 1 by the booster line and 1 by the T from the 3/2 valve.

They look like just a little vacuum hose connector. You will only see a little strip of plastic between the two hoses.

You got it! :D

Part Number?
 

I can't find these on the site for sale. Is there another name for them or do you have a part number so that I could order a couple from mercedes?

Thanks

hopeless MB dealer
 

Well the can't find any orifice or the like at the local mercedes dealer. Apparently this is a phantom part!

I'm beginning to have less and less faith in the MB dealers parts desk! (Let alone their mechanics!).

Also he said the green dashpot is only one way! Is that correct?
Update:
Strike 2 for the mercedes dealers. I think I'm going to have to buy via mercedesshop, ship it to family in washington and then go there because this is absolutely ridiculous.
I can't even get anyone to find the piece. Help! If anyone can get me a picture or the part (this black orifice) please!

Your vacuum orifice posts sure give me hope...
 

I'm a newbie who was just about to give up on my 1980 300D's trannie and this thread came in with my first ever e-mail delivery from the forum. I told you I'm a "newbie". Despite some of your replys being a bit criptic, I think I followed them... thus the hope. What I I feel I need most right now is to get my hands on what I know is a "spec" vacuum diagram for this recent purchase that I'm trying to make work well enough to turn over to my Son. I've got an e-mail into M-B USA tech people but thus far no response.

Can anyone out there put me on the right path to find the correct vacuum diagram... the one for trannie shifting problems ?

Sam

Welcome to the forum, Sam.

I believe that this is very close to your vacuum diagram..........provided that you don't have EGR:


http://home.comcast.net/~phantoms/vacuum/engine.jpg


Please compare the diagram to your vehicle as the diagrams that we have on the forum are generic and may not be exact for every model.

Vacuum Diagram for 1980 300D with EGR ?!
 

Brian,
Your prompt [ literally overnight for me ] response to my plea regarding a vacuum diagram… well it harkens me back to one of the many required memorizations I had to learn as a Plebe at the academy:
“ No soon said than done… so acts a man of worth ” ! And I had to learn that little “diddie” in 1964 and up it popped from a lot of cob webs !

However this 1980 300D does have an EGR valve ! I think these 1980 models M-B(s) were subjected to some kind of internal purge within the R&D group at M-B and this explains why I’m having such a hard time coming up with more certainty in this and other searches for answers. I also have a 1980 240D which had a dealer install engine with only ~13K miles on it... and does not have an EGR valve.

Do you or anyone else know if one can expect results if I were to go to the local parts department of my local M-B dealer armed with the VIN #... would this likely result in my obtain an " official ” vacuum diagram? I suspect that your's is probably close Brian... and I have others that show how the EGR is connected so I think I'm on the right path now. I have a new vacuum tester coming soon so hopefully I'll be able to sort out this vacuum thing here soon.

Brian, your response has made me feel like I have arrived at the inner sanctum of this DIY's forum… thanks,

Sam Ross

Sam, you have me in a quandry with EGR on a 1980 vehicle.

But, check out the diagrams that we currently have on the forum and see if any of them make sense. Personally, I didn't see any diagrams that were suitable..........most were for later models..........but...........you never know.........


http://www.peachparts.com/shopforum/showthread.php?t=105297

Sam,
I had an '80 300TD (wagon), and I can tell you one thing. 1980 is a very inconsistent year. There were more than a couple of changes "cut in" in 1980, which is why it is often described as a "transitional year" for these cars. The vacuum systems, the change from climate control II to climate control III are a couple of the examples.
I would recommend you dig into the search function of the archives and read posts and peruse some of the pictures. Learn which line does what, where it goes, etc... and you can solve the mystery of your vac issues.
One thing to note: into the firewall, next to the brake booster, some of the vacuum lines go though a rubber thing. Vac lines are color coded thusly:
yellow----door locks
yellow/gray-----vac reservoir for door locks
Green/yellow-----climate control vacuum (if you have climate control II this might not apply, I'm not sure (climate II has vert. buttons, climate III has horizontal)
Brown-----key switch for shutoff vacuum
black-----just a vent line that hangs under dash

You can isolate one circuit at a time, if need be, for trouble shooting purposes. A golf tee and some extra vac line will help.
Keep us informed of your progress, and any additional help we may offer.
Welcome :)

**edit**
The post below has the diagram that matched this wagon.

300d diagram
 

I think you'll find that this is your diagram. It's a lot simpler than you'd think. It doesn't include the door lock diagram, but if you're having trouble with that part of the system PM me today (I'll be away from my computer for next week) and I'll send you some troubleshoot notes for it.

BTW I ordered the dashpot, but no help from the dealers on that black orifice.