I plugged the EGR line.

Hooked a Mityvac in on a T going to the transmission line. From a cold start, slow build to 10 mmHg then steady while driving at constant speed, pressing the accelerator yielded a rapid drop to 0 (almost instantly) and then it'd build back up fairly quickly

VCV held 14 mmHg with almost no drop with the engine off; moving the rack caused instant drop to 0.

Shifts are still too early and very mushy. I am thinking the problem might lie in all the complicated stuff on top of the valve cover, maybe the lever up there is worn down in some way, its leaking internally, etc.

Disconnect the vacuum line from the transmission (you can do it under the hood). Plug the open line on the supply side. Leave the trans line open.

Take it for a drive and see what it does with no vacuum.

Report back.

Will do when its light again.

Brian can you give me a quick run down because reading this whole thread got me confused!
My problem:
1.Car (85 300DT) will shift fine from 1-2 BUT will JERK BADLY from 2-3. Also downsifts from 2-1 with a BIG THUMP HORRID noise.
What should I start checking first? What are the steps here?

Disconnect the line to the modulator.

Connect the Mityvac. Pump up the Mityvac and see if the modulator holds vacuum.

If it does, then remove the Mityvac and reconnect it with a T into the modulator line so you can read it with the engine running.

Start the engine and read the vacuum at idle going to the modulator.

Report back with results.

Hard and late. 1-2 at 15, 2-3 at 30, 3-4 at 60. Just as it was before I found and plugged a vacuum leak before the line that actually goes to the transmission.

So, we've determined that "no vacuum" makes it shift like it used to (****ty as all hell) and "good vacuum" makes it shift WAY too early (1-2 about 1 second after it gets gas, <5 mph, 2-3 at like 20, 3-4 at 35 or so -- and it also "slips" and revs randomly for a second then quiets down again. Never does this in the "no vacuum" condition.)

Have I narrowed it down to the modulator yet, or should I try replacing the crap on my valve cover entirely first? (3/2, levers, internal lines) they look pretty beat up.

Very good.

So, we know that we can get the desired results with a vacuum adjustment.

Now, I'm not personally familiar with the 616, but we need to determine if the VCV on the IP is adjustable.

Please look at the VCV and tell me if it has a small domed cover on the forward end (closest to the radiator). The domed cover will be facing the left side of the vehicle (facing you when you're looking in there).

Nothing needs to be done with the modulator and nothing needs to be done with the 3/2 valves............just get that out of your mind completely and don't touch anything else.

Is the modulator the white piece on the IP?

The modulator is on the side of the transmission and regulates the speed of the shifts. The VCV is on the IP and regulates the vacuum level to the modulator.

Can someone define "flare" for me - I think that's one of things my tranny's doing. It kicks - really, really bad when cold - from 1st to second and the remaining shifts always seem like it's saying... "I'm shifting now, really, I am shifting now, honest, see I'm shifting" before it finally does a soft slide into gear. Does that have a name?

Is this the vacuum diagram for my 1985 Diesel Turbo??

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

Ok, so I located the VCV and the modulator on the tranny.
TO disconect the line at the modulator...well the line looks to me that it hooks from the vacuum damper(number 72 in the picture) located on the transducer to the AT modulator??? Am I on the right path here?

Yep, that should be your diagram.

Correct, on the '85, the line to the modulator originates at the "TRA" port on the top of the "vacuum transducer"...........also referred to as the "blue flying saucer".

Dude, you're probably the most helpful person on here. I very much appreciate the work you're doing for us with transmission problems.

Will post the results of a 616 VCV inspection in daylight.

Anytime. Just continue to follow suggestions on the thread and we'll sort it out. Many folks give up in the middle due to other more critical items........or just the lack of time.

Ok so here is what I got done today:

1.Disc the vac. line going to modulator. Well to my surprise it didn't hold vacuum at all. After messing with stuff for some time, I discovered that the line was cracked. Well I temporarly fixed it by cutting the line and hooking up a silicone vacuum line over it, and there it was a world of difference. My pump went to 25mmHG and it was staying there. That is a good sign because the modulator can hold vacuum right? Well my next question is how in the world my hand is supposed to fit and get to the modulator to change the old vacuum line?
2. I got called in to work and I had to quit for the day. Eager I hooked everything back up and took off. I did see improvement shifting, all shifts are really nice and crisp except 3rd(really wimpy and soft like always).
No more HARD banging shifts in 2nd!!! Well coming to a stop sign shifting from 2nd to 1st it SHOOKED really hard just like before.
What I don't understand is that sometimes when it downshifts from 2 to 1(10mph less) it does jerk really hard and sometimes it doesn't!!

What should I be checking next???

Ohh...I also discovered I got a tiny oil leak while I was under the car today. It won't leak while it's running/idle?? Only after it sits for 10 min??I can't locate the leak bc it looks dirty as is under the engine. Any ideas/suggestions?

I have no confidence in your temporary fix. When you properly replace the vacuum line from the vacuum transducer to the modulator, we can go forward. Until then, who knows if it's holding vacuum more than a few minutes. I may have worked for 10 minutes and failed again.

Since this line is compromised, it's likely that most of your vacuum lines are NFG. A vehicle of this age requires all of those lines to be replaced otherwise you'll never fix your issues.

I believe it does, see attached.

In the first picture, it's the pointy domed thing on the front of the VCV, near the black T connector? Its on the left side of the device, closest to the radiator.

The dome is in the second photo.........just "above" and to the "left" of the vacuum line.

See if you can carefully remove this dome..........you'll need an exacto knife to pry it off the housing. After you do this, take a good photo of what's below the dome and post it.

Newbie Posting from England
 

Hi all have now read this thread from the beggining makes very interesting reading, here is my situation, I have got an 82 300TD w123 in my care at the moment, I have been entrusted to convert it from a four speed manual to an auto, I fixed up the tranny which was a donor from an 81 sedan (we call them saloons on this side of the pond) put in new fluid, gasket and filter. I took the VCV from the 81 donor car (metal type) and put a new 3:2 valve on the cam cover, this car being european does not have an EGR setup is non turbo and does not have AC or climate control so a fairly simple setup, I have no vacuum leaks whatsoever in the rest of the vac circuit central locking, shut off etc is all on new hose and all the t-pieces and joining sections are also new, The line to the modulator holds vaccum when pumped from my hand-held vaccum pump, I bought all the orafices suggested here and have tried placing them randomly in different spots round the circuit but they do not make any difference I still get 25 HG at idle every where dropping to 15HG under load, The tranny is of the older type with the smaller sump-pan and the lockout/reverse light wiring aranged vertically, the closest diagram on here to my setup is this one http://home.comcast.net/~phantoms/vacuum/engine.jpg but not exactly the same as the euro spec is obviously different. My shifts are all very late although when the engine is warm and I adjust the throttle linkage I can get them acceptable although still late, as soon as I start again from cold I am back to square one. I note that the reading is supposed to start out at 10HG and drop to 0 at full throttle, the only way I managed to achieve this is to wind the throttle linkage in so that the 3:2 valve is partially depressed I am not sure that this is right, so here is my question, On the diagrams for automatic transmission the brake booster hose has two outlets, Is this type of hose designed for automatic transmission specifically? my brake booster hose only has one outlet and measures 25HG on the vaccum pump, Does the secondary one upstream reduce the vacuum output at the hose? Could this be my problem? Hope you knowledgeable folks over there can help me because talking to a parts guy in an MB dealership here is about as useful as an ashtray on a motorbike :) many thanks in advance

Felix

NOOOOOOOO!!!!!!!!!!!!!:eek: Most want to go the other way.

yup Im with you on that on Chad personally I would go manual every time still the customer is always right as they say :)

Hello from this side of the POND...
 

Felix... hello from someone who the geneologist say is a Scottsman ["Ross"] but from my Mother's side my middle name is "Millsaps" which is pure English! So hello relative!... now to your situation and questions.

I started this THREAD/subject because I felt, and still do, that the restricted orifices are NOT understood... and eventually I came to believe that they are an easy 1st step for MBz to put the vacuum shifting control system in rough balance... to get the pressure being delivered to the vacuum line that branches to both VCV and Modulator... to get the vacuum at this point to approximately the right value. We can debate what that value is but I think ~10" is probably as good a # as any. I think this number is a variable depending upon what generation of both VCV and modulator you have.

So in your case having only one vacuum "T" branching off the pump-to-booster chamber line, I think I would first probe the inside of your "T" and see just how large the internal opening is... and IF it is less than 1.5mm, then I would consider widening this while being careful to NOT degrade the strength of the "T". This will give you the greater vacuum capacity I think you will need through the single "T"... capacity for both shifting control as well as the door-lock system(s). Without aa ACC system with 5 leaky vacuum elements, you can probably get by with the single "T" connection.

So then you could use one of the rubber "Y" vacuum connectors to branch off and somewhat separately supply vacuum to:
(a) the auto-shifting tranny control system, and
(b) the door-lock system(s) as presently plumbed.

In each the new and separate branches, you can add whatever size restricted orifice you find you need... and I would first start by restricting the vacuum drawn from the door-lock systems as much as you can and still have these locks perform reasonably well.

On the "Tranny-shifting" vacuum branch you might want to use the small neetle-valve idea someone recently shared with us on this THREAD. I still want to try this myself but I want to find the right needle valve that is small enough and has the needle tip tapered raw brass and now the rubber tipped type that are used to supply the ice-maker accessory we put on our refrigerators in the U.S. With such a adjustible needle valve, you could adjust the tranny-shifter system at idle until you get the lower vacuum reading you need where the VCV and Modulator lines come together. I trust you fully understand that there are different style VCVs but to my knowledge ALL are adjustible to some degree... and what you are doing is increasing/decreasing the tension/compression on an internal coiled spring that is acted upon by the VCV's mechanical link to the Injection Pump's (IP) throttle linkage... thus the VCV helps to increasingly "BLEED-OFF' the vacuum being seen by the Modulator. I LOVE run-on sentences... I write like we talk!

I hope this helps... and I'll continue monitoring this THREAD/Subject so his us with any more questions you have.
Regards - Samuel " MILLSAPS " ross !

Thanks for your answer Would I be right in assuming that we are dealing with negative pressure here ie suction therefore the wider the opening the lesser the vacuum at the guage ? I have a spare brake booster hose so have some room for experimentation, how likely is it that by drilling out the tee section my reading will reduce, what size drill bit would you reccomend? as far as the locking secton goes the yellow valves are non return right ? so with minimal leakage on that side the resevoir will fill and stay full enough of vacuum to still operate the locks regardless of the desired drop in vacccum for the tranny ? as concerns the needle valve suggestion I am not sure where to get such a device, does this act as an extra bleed or is it just a tap which increases the vacuum when locked down,Would a syphon tap such as you might use for beer making work? again I assume the smaller the gap the bigger the increase on the guage, look at me I am writing very long sentances now thanks again

Felix

There needs to be some futher tests before you go off and start randomly changing orifices.

First, does the vehicle have a vacuum control valve.........white plastic valve at the rear of the IP.........controls vacuum to the transmission?

If yes, please disconnect the hose from the top of the valve and connect the Mityvac. Pump up the Mityvac (engine not running) and record the reading at idle. Report back with results.

the vacuum control valve has a metal housing with a circular plastic housing on the top this has two vac feeds on the top, car is in the body shop till thurs but will try as you suggest then, I will also post some pics of the various vac parts too

Felix

With two vacuum feeds on the top of the valve, it's radically different from the same unit over here. So, a photo will help..........but, the routing of those two hoses is critical to understand the function.

Felix,
As the Original author and starter of this THREAD/subject, I hope YOU have sensed from my past POSTs on this THREAD that I am NOT the type of Engineer who advises readers to "RANDOMLY" do things! ........ Mr. Carlton certainly has a right to his opinion as to the function of these orifices so it's up to YOU to choose the advise you want to take... which is your right too! Brian obviously has a great deal of knowledge on the subject of these vacuum shifting systems so please do NOT think I am suggesting you disregard his writings!

I read your first POST fairly closely and now I will repeat your last POST and try to answer the questions you obviously still have. My comments will follow below:................ SO LET's GET TO YOUR LATEST QUESTIONS !!!
====================================================
Thanks for your answer.
Q1 - Would I be right in assuming that we are dealing with negative pressure here i.e. suction therefore the wider the opening the lesser the vacuum at the guage ?

My answer to Q1 - Yes and No... I don't see where there is anything such as "Negative Pressure" but IF it helps your understanding, that's one way to think of it. I see it as pressure that is less than atmospheric... or for you there in foggy England less than 1 BAR!

Q2 - I have a spare brake booster hose so have some room for experimentation, how likely is it that by drilling out the tee section my reading will reduce, what size drill bit would you reccomend?

My answer to Q2 - Here is where [to a degree] I agree with Brian, IF you start drilling out the " T " in the main Pump-to-Booster line, you might drill out too much right off. Just as I uggested before, I would first install the " T " and connect the two separate branches [ tranny shifting & lock-out] and then monitor the vacuum at idle in each of these branches BEFORE you do any drilling! Then IF you still see high vacuum readings in the tranny-sifter branch as you increase throttle, well then I think it's time to put one of the smaller orifices in that branch only... and check the vacuum again [toward the tranny-shifter side].

I think a Sidebar is Needed here - Try thinking of a normal pressure gage as measuring the pressure above BAR/atmospheric and a Vacuum Gauge as measuring the pressure below BAR/atmospheric (14.7psi). In vacuum system plumbing such as this, I also find it easier IF one stops and thinks of what direction the air is actually flowing and in this tranny-shifter system, the bleeding effect of the VCV means that when the VCV is open, air is regularly flowing from the atmosphere through the VCV and the amount of this flow increases as the throttle is increased... and as you let in more air, the pressure increases but the vacuum increases.
So now to try and apply this abstract thinking to your question - Anywhere there is a restriction [ at the " T " or an in-line orifice] and there is no air flowing inside, it does NOT matter where you measure the vacuum...for you will get the same reading... it is when the air starts flowing that you begin to see different readings at different points in the plumbing and you will read a lower vacuum reading [higher absolute pressure reading] the further "upstream with air flowing" or put another way the further you get from the source of energy that is creating the vacuum [the vacuum pump]. IF you increase the size of the opening in the resriction, the vacuum will increase the flow "UPSTREAM" of the restriction IF you just stop and think of how the air is flowing inside. In a "dynamic" [air is flowing] system such as this, I think this method of thinking helps for in fact [if the VCV is open and air is flowing] increasing the size of the opening at any such restriction would in fact increase the vacuum you measure "Upstream as the air flows". It's a bit abstract and I often have to stop and think through the situation... and that is to think of how the air is actually flowing inside. I hope my SIDEBAR discussion helps !

Q3 - As far as the locking section goes the yellow valves are non return right?

My answer to Q3 - " YES " if by " yellow " you mean one of the check valves that is needed to retain and isolate vacuum in the car's reservoir!

Q4 - So with minimal leakage on that side the resevoir will fill and stay full enough of vacuum to still operate the locks regardless of the desired drop in vacccum for the tranny?

My answer to Q4 - I think I understand the question... and YES you very much want to have sufficient isolation between the tranny-shifter system and the door-lock system... and this is why so long as you stay with a single " T " off the main, large, pump-to-booster vacuum line... it might be necessary to use the ill-understood restricted orifices... maybe in both branches.

Q5 - As concerns the needle valve suggestion I am not sure where to get such a device, does this act as an extra bleed or is it just a tap which increases the vacuum when locked down,Would a syphon tap such as you might use for beer making work?

My answer to Q5 - I too have a problem finding a reasonably priced "needle valve" here in the U.S. The rubber tipped valves are readily available on the hardware/plumbing stores in 1/4-inch size [~6mm] but the open too quickly and do not give me the ability I want to fine tune the vacuum in the tranny-shifter system.

Q6 - Again I assume the smaller the gap the bigger the increase on the guage?

My answer to Q6 - Not sure of your meaning by this mate, but once again, IF you think of the air flowing through the needle valve [toward the vacuum pump]... and IF you are measuring vacuum " Upstream " of the neadle valve, opening the needle valve would increase the air flowing through it and YES increase the vacuum gauge's reading. Think of vacuum this way and it's harder to go wrong!

Look at me I am writing very long sentances now thanks again --- Felix
=============================================

Out of here mate - Regards,

thanks Sam have printed the last few posts and will attempt to get my head round them over the next couple of days The car is back on Thursday at which point I shall no doubt be back in touch with some pics, thoughts and hopefully some results :)

Felix... back to your last Question...
 

Felix,
After I looked at it later, I came to NOT like my answer and explanation above... let me try again!
My response above now appears contradictory to me. What I meant to say was that you were wrong to think the gauge would increase with a smaller restricted orafice or closure of the valve... but what I said was "YES" the vacuum would increase [UPSTREAM] IF you increased the size of the orafice or opened the valve and I don't want to confuse you. It's a good idea to always stipulate where you are reading either pressure or vacuum when you say take a reading!
Best regards,

Well here I am again with the car back in my possesion, I have taken some photos of the vaccum parts within the engine bay and labled them as to what they do, does this look right or have I done it completely wrong? I have not yet drilled out anything and the car is still shifting very late almost red-lining,

when I plug my vaccum guage to the point where I have labled "to transmission " I get 25 inches HG unless I wind in the throttle cable so that it partially engages the 3:2 valve This then reduces the reading to 10HG at idle hopefully you can see this in the 1st picture

I have also tried reversing the hose layout so that the cable to the tranny come off the right-hand outlet at the VCV but this makes no difference, the reading does drop when I increase the throttle but still gives me late harsh shifts, this message is basically the same as my first but this time with pictures to illustrate my setup, the orafices are on the bench in the workshop at the moment a red one, a green one, a yellow one and a blue one, thanks for taking the time to read this hope you can help

Felix

Unfortunately, the setup that you have is completely different than the '82 300 turbodiesels that are over here. Therefore, it's extremely difficult to point you in the right direction due to the lack of a proper vacuum diagram.

My guess is that the vacuum of 25" is exceptionally high and needs to be approximately 13" for the transmission to shift and perform properly. You can verify this by connecting the Mityvac directly to the transmission, pump it up to about 13", route it into the vehicle, and drive it. See if the performance is what you need. The Mityvac will probably need to be pumped up periodically to maintain the 13"..........hence the need to route it into the cabin.

At least we can confirm what will solve the problem. The hardware issues to actually get it done are more difficult without a proper diagram.

this would be with an assistant pumping it to keep it at 13" whilst I am driving presumably I will attempt this tommorow :)

13" is not absolutely critical. You can even try it at 10" and see how you like it. At greater throttle positions, the value should be reduced toward 5" in normal operations............finally getting close to zero at maximum power.

You ahve a different kind of VCV "beast" !!!!!!!!!!
 

Felix,
Although I have NOT spent much time looking at your photos and researching this YET... but my initial take is that Brian is correct, YOU have a very different "beast" or VCV there on your side of the "POND" ! Until I can get back and spend some further time on this, I recommend you take a look at these two links:
1/ This is a typical VCV for a 1982 model 300D Turbo here in the U.S. - Note the valve is all plastic, and has only two vacuum connections.
http://catalog.worldpac.com/mercedesshop/sophio/image.jsp?title=Inj.%20Pump%20Vacuum%20Valve&url=http%3A//img.eautopartscatalog.com/live/D203215990OES.JPG
2/ This is from the Peter Schmid transmission rebuilders near to me here in San Francisco and shows the various vacuum diagrams for the tranny-shifter vacuum control systems. http://www.peterschmid.com/1984.htm
Go to this site and look at the two options for 616 & 617 engines. IF/when you decide which vacuum diagram there is best for you, then let me know what its link address is and I'll probably be able to " loan " send you a clearer copy of the diagram!

I have the complete set of W123 manuals now [on computer CD(s)] so maybe I can get a clue as to the obviously metal version of the VCV in your photo.

Q - Can you tell us what car your VCV came out of?
Regards,

Hi the VCV came from an 81 Sedan same car as the transmission, Interestingly Steve brotherton shows a picture of it in his article its the one in fig 3 here http://www.continentalimports.com/ser_ic20242.html, none of the Shmid diagrams bear any similarity to my setup really, the only one that comes close is the one on this very forum here http://home.comcast.net/~phantoms/vacuum/engine.jpg this is the one I went by when I set the vac system up, obviously my car does not have item 1 and 2, It is a strange thing, I feel I am very close to a solution but just must be missing something, What do you think would happen If I did away with the VCV I have and ordered the plastic type mentioned on the US diagrams? just a thought.

No thats a silly idea he said answering his own question :) The turbo diesel was never made in Right Hand Drive because The steering box is in the way of the turbo, the plastic VCV is designed for the turbo diesel setup so I dont think that would work, Were all 300D cars in the US turbo diesels or did MB export a non turbo version? There just dont seem to be any diagrams available for the UK version of the TD auto, I think 90% of the uk 300s and 240s were shipped with manual, however auto was an option so how did they do it ? I carry on wondering :)

That VCV is identical to the VCV found on the later turbodiesels. The 603 engine uses the identical unit. Vacuum is supplied via one of the top ports and is sent to the transmission (or the vacuum transducer) via the second port. The third port near the bottom is the vent.

The problem may simply be the lack of an orifice in front of the VCV. The VCV is not capable of dumping unlimited vacuum, and without any orifice, the vacuum levels will be much too high.

I think you are on the right track.............!!!!!!!111
 

Brian - Whatever the design of this newer VCV is , I agree that a restricted orafice is needed. Thanks for recognizing this VCV as being from the newer cars and thus this would explain the different plumbing of this tranny control system.

Felix - I would start with the small orafice that you have and place it in the tranny-shifter line immediately where it first branches off from the rubber "Y" connector you installed to separate the tranny-shifter plumbing from the door-lock vacuum plumbing! Then read "T" OFF "DOWNSTREAM" as necessary to allow you to monitor the vacuum on the tranny-shifter side of this restricted orafice ! Report back what you see.

I think we are on the right track for it appears to me that the VCV system you have... this VCV incorporates the bleeding off/down of the vacuum internal to the body of the VCV and then this reduced vacuum is sent/sensed by the vacuum modulator on the tranny! But first let's see IF you are sending your VCV a lower vacuum pressure?
Best regards,

Let me add a SIDEBAR correction about something.......
 

Felix,
The plastic style of VCV that you speak of... this style is very common to MBZ(s) here in the U.S.... I believe starting in 1980. Both of our W123(s), the 240D and 300D have this same VCV and these cars are NON-turbo... and YES NON-turbo cars are quite common here!

Regards,

Back again !
 

Hi again, have given this a couple of hours today and this is what I did

I routed the line from the modulator through to the inside and kept the vac pump on it and yes the upshifts are a lot more favourable, of course the downshifts dont change properly and the box slips in the higher gears but yes this seems to prove that the level of vacuum is indeed critical i noticed that 8 " gave me harder shifts and 15" gave softer ones does that sound right? So a good suggestion and proves that its how I get there that is important.

next I re-plumbed the rubber y junction from the main tee such that CL headlight adjust and engine shut off are on one side of the Y (with a non return valve for good measure) and just the tranny line is on the other. A vaccuum reading on the tranny side gives me 26" so I inserted a restricting orafice and the reading is still 26" I tried all four of the orafices in turn and all seem to have no effect I even tried them in-line with each other but to no avail, shouldnt the orafice reduce the vacuum reading?

Something else I need to clarify, When I start the engine and hook the guage up to the Y piece I get a reading of 13" when I rev up the engine to high revs this jumps up to 26" and stays there when the revs decrease in fact it stays there till I turn the engine right off disconnect the guage and repeat the process is this as it should be?

I think what I need is a drastic vacuum reducing measure at the Y branch but not sure exactly what,

thanks again for all your time taken to answer my questions

Felix

... Remember unless air flows... there are no vacuum pressure drops !
 

Felix - let me list and disect your last POST... and make comment [boldface & underlined] following each section of your POST :
[1] - I routed the line from the modulator through to the inside and kept the vac pump on it and yes the upshifts are a lot more favourable, of course the downshifts dont change properly and the box slips in the higher gears but yes this seems to prove that the level of vacuum is indeed critical i noticed that 8 " gave me harder shifts and 15" gave softer ones does that sound right? So a good suggestion and proves that its how I get there that is important.

Yes I have heard of doing this but not tried it yet... I can see where this would be a real moral booster when someone is thinking they might have to replace a tranny that does not shift properly... and this should give you some idea as to just how low the vacuum readings need to be in order to see the tranny strart shifting as you want!!!

[2] - Next I re-plumbed the rubber y junction from the main tee such that CL headlight adjust and engine shut off are on one side of the Y (with a non return valve for good measure) and just the tranny line is on the other. A vaccuum reading on the tranny side gives me 26" so I inserted a restricting orafice and the reading is still 26" I tried all four of the orafices in turn and all seem to have no effect I even tried them in-line with each other but to no avail, shouldnt the orafice reduce the vacuum reading?

Here is where I must remind you that until there is air flowing into the tranny-shifter vacuum control system... until this happens via the VCV bleeding action, you will NOT see consistent lowering to any great degree of vacuum readings in the tranny shifting system!
So maybe the VCV "Vent" port that is down low on the side... maybe this is plugged up or maybe the VCV is plugged internally. Put your hand vacuum pump onto the upper "Bleed" port of the VCV and pump to see IF you can draw a vacuum through the VCV... and you judge this by placing your finger on the "Vent" port on the lower side near the bottom of the VCV. IF you get no vacuum suction on your little "pinky finger", then the VCV is plugged or partially plugged and should be dissasembled, cleaned with solvent and blown out with air... this baby can easily co$t ~$100 to $200 USD new!

[3] - Something else I need to clarify, When I start the engine and hook the guage up to the Y piece I get a reading of 13" when I rev up the engine to high revs this jumps up to 26" and stays there when the revs decrease in fact it stays there till I turn the engine right off disconnect the guage and repeat the process is this as it should be?

Is there a check valve between your point of reading and the vacuum pump? IF there is NO check toward the vacuum pump, maybe the check in the other plumbing branch is leaking and thus effectively maintains the artificially high vacuum readings by sucking air into the fully charged vacuum reservoir when the engine slows down... otherwise this is more than a little bit STRANGE.

[4] I think what I need is a drastic vacuum reducing measure at the Y branch but not sure exactly what.

While doing your vacuum reading test, use pliers to gradually pinch off a section of flexible vacuum line to prove that you are able to close off the air flow and thus create the reduced vacuum... but remember there MUST be air flowing into the system from somewhere... the VCV needs to be bleeding or air must be leaking into the vacuum system or you will NOT see as much vacuum reading reduction in your readings... at least not as much as you might think there should be.

Regards,

Went to replace the front wings today with newly painted ones took the old ones off and found loads of rot in the inner wings so have mostly been active with grinder and mig-welder this afternoon, have in my mind to invent a vacuum reduction/bleed device from a Copper gas Y valve that they use for temporarily re/routing gas supplies in flats here , 2 reducers from 15mm to 8mm two from 8mm to 3mm and some creative soldering watch this space :)

Some of the official MBZ plastic orifices are smaller than 1mm !!!!
 

Felix,
As my subject line above implies, I think you are going to need an even smaller restriction in the Tranny-Shifter Vacuum Control System branch of the plumbing you are building and these small orifices can easily get clogged!… and this supports another of my recommendations for these systems… namely to install cheap clear plastic in-line paper media gasoline fuel filters at/in:

[1] in the line that runs from the VCV’s “Vent” port and then thru the firewall and is left open under the dash!,

[2] in the line that runs down to the tranny vacuum modulator, AND

[3] in the line between the IP shut-down vacuum box and the ignition key/vacuum switch.

Further, I recommend that these two clear filters for [2] & [3] above be positioned under the hood in locations that they can be readily seen… so they will serve as a “tell-tale” and be seen... the very black engine oil that can leak from a ruptured diaphragm at the IP shut-down box [3] and the often very red fluid that can leak from a ruptured diaphragm at tranny [2] (a rare occurrence I hear)!
Regards,

Newbie searching old threads finding good stuff
 

OK, I finding a lot of information that is helping be resolve problems I've endured with my 1983 300D turbo over the entire life of the car. I bought it new in 83 and the transmission totally failed before 100,000 miles. The rebuild was done in an independent shop but it is still going strong at 203,000 miles. It has always had a hard 1-2 shift, followed by a quick 2-3 shift, and a very delayed 3-4 shift. Reading these old posts makes me think I should do some vacuum work. Emission testing is not required in Texas for this car. I have the black box described here and can see how to eliminate the two lines on the driver side. There is a third line that goes to a fitting on the right front of the engine (temperature sensor maybe?) then a line comes out next to it that goes to what I think is the EGR valve. What can I do, if anything with those lines?

Brown line through the firewall is CC, right. Remove and plug that while I test the transmission readings? Where does the K1 transmission spring kit go that is mentioned in another thread or is that not for my model. Looks like I have a cable controlled kick down system.

I appreciate any suggestions or links to other threads that anyone can offer.

Charles

There is often more than one way to describe something...
 

Charles - I'm forced to speculate that your 1983 300D is actually either a European car, a 300D-T, a 300TD or 300CD for in 1983 I don't think the 300D was imported to either the U.S. or Canada. My reference tells me that all of the 300 series diesels [above] delivered to the U.S. in 1983... all of these were turbo equipped and had the 617.952 engine. Does yours have a turbo? This is important because we need to have a diagram... the the proper "tranny-shifter vacuum control diagram" to reference and work from. IF you have the 617.952 engine, then your correct diagram is probably this one at: http://www.peterschmid.com/vacuum/1977_1985/617_95/1981_1984.jpg. Do the SEARCH/research and confirm whether or not I am correct about your model... and IF I am correct, look at the diagram addressed above and confirm whether your car's "tranny-shifter vac. sys." matches the diagram!

When I read your repeat from Brain Carlton's 2006 POST, I just have to highlight some of his expressions that I think are another way to try and explain away some of the confusion I often see on this THREAD... confusion about a vacuum system that is designed to be "static" [no air flowing] at idle and then becomes "dynamic" [with air flowing] when the throttle is first opened and becomes more and more "dynamic" as the VCV is opened allowing more air into the system... thus lowering the vacuum readings. Take a look below:
=======================================================
Originally Posted by Brian Carlton
The orifices have no direction. They are simply a narrow plastic tube with a specified inner diameter.

You[r] vacuum at idle should be less than 15". Somewhere around 10" would be preferred. I've got the SD set at 8" and the shifts are crisp but don't bang.

The orifices control the flow rate. Under a steady state condition, they have no effect. But, since the VCV works via a bleed, the orifice serves to control the amount of flow to allow the VCV to attain 0" vacuum. Without the orifice, the VCV could not leak sufficient air to reduce vacuum to an appropriate level.
=================================================
Above, I can readily see now that Brian Carlton is saying the same thing I have been saying for some time now and beating horses to death about [about dynamic -vs- static states in vacuum systems ]... it's just that Brian's explanation is different from mine!

Charles... also explain what you mean by "Brown line through the firewall is CC, right."? I believe the brown line is supplying vacuum from the ignition switch back to the "vacuum box" that shuts-down the IP.
Regards

The third line goes to the temperature controlled vacuum switch. Just pull this line off and toss it. The line that comes out of the switch does go to the EGR valve, as you guessed. Just pull that line and toss it. No plugs need to be put in place on the valve or on the switch...........if you've already removed and plugged the vacuum supply line to the black box.

Personally, I don't believe that vacuum will solve your problems. The 1-2 has always been too firm up until about 1984 when the spring was changed. The stacked 2-3 can also be a problem on these units. Some folks have had success with the Superior shift kit that addresses both these issues with a change of springs.

Yes, separate/simplify... and then it's easier to work on...
 

Brian,
I agree with you that "Cr from Texas" should cut out the "Black Box" from his system... but only just for now. This will make for a simpler "Tranny-Shifter Vacuum System" allowing him to resolve [as much as practicable] other vacuum leaks and/or defective components and to clean and make adjustments [thinking mainly of the CVC] where needed... and of course once these are complete he will want to likely "tweak" the tranny modulator. Once the car is running the best he can tune it, then he can decide upon the tranny spring kit to whatever benefit that might offer. I have a Kit still unused that he can have for the cost of postage!

Then he can come back and look at any problems that might exist with the "Black Box"... this in order to try and add back in the idle and high RPM refinements the "Black Box" potentially offer. Yes he can live without the "Black Box" but I think it's worth coming back to later.

"Cr from Texas" - Have you ID'd the model and vacuum diagram for your car. IF NOT, give us the VIN and we can SEARCH on that to resolve these questions??
Regards,

Brian and Sam, Thanks for the quick replies
 

I'm so glad I found this forum. I was on the verge of giving away my 300D after 25 years of service. Finding this forum has totally reversed my position. I'm keeping it! I've removed the trim and the windshields for a repaint. It won't be driveable for some time so I'll be limited in my ability to diagnose the tranny. I really appreciate the time and dedication you are giving to this forum.

The car is a USA model 300D 4 door sedan with turbo bought new by me from the Mercedes dealer in Dallas in 1983. This is the plate information:

DOOR PLATE:
04/83
WDB AB33A6DB031332

ENGINE BAY PLATE:
3076497
123133 12
4E 1
06699 410 504 593
104585 440 519 639
0 451 531
2 737 G 467 546
491 588 803

I've lived with the shifting issue for years. I've also lived with climate control issues for years. Trips for repairs have been of limited help. Reading this forum makes me think the two issues may be connected and related to vacuum.

I thought the brown line was the vacuum source to the climate control (CC) system. I've got a mighty vac and when the car comes back from paint I will begin to diagnose issues with the vacuum system. Doors lock properly so that part of the system seems to be OK. When the car is back from paint, I need to diagnose the climate control vacuum circuit before the tranny as I removed the windshield for painting and will removed the badly cracked dash (I found a better one - still looking for crack free - may do the hard plastic cover) in preparation of fixing climate control issues.

Since emission control is no longer an issue with this car, I'd like to get the best performance from it. What do I loose if I permanently eliminate the black box? Tossing the EGR line leaves it in the best position? I'm pretty sure one of the cables near by is for the tranny kick down control. I guess that will be the last adjustment.

I think I'm following this thread properly. Only some of the information will apply to my model. If this is the model that can benefit from the spring set, I'd be a fool to pass up Sam's offer. I'll send you a private message and we can work out payment and shipping details. Do I drop the pan to put in this spring or is it external to the tranny?

Thank you for your help,
Charles

The box must physically remain in place, but you can remove all lines to and from the box. It only controls EGR. However, you must be sure that the vacuum supply line..........where it originates from the T..........is plugged at the T. Or you can just eliminate the T. Make sure you don't develop a vacuum leak or the transmission shifts will go to very firm in a hurry.

The box only controls EGR. The Bowden cable connects to the throttle linkage on the right side of the head near the rear. It can be adjusted to delay the shifts if desired. But, it delays all of them..........not any one individually. If you want to experiment with it..........turn the black plastic adjusting nut clockwise to tighten the cable and delay the shifts. Turn it two turns and take it for a drive..........see if it helps or hurts. You can also go counterclockwise to make the shifts earlier. It puts more slack in the cable.

I'll have to wait
 

Thanks Brian,
I'll have to wait till the car is in a more driveable state and get back to you. I assume vacuum first then Bowden cable. Sam suggests I could loose some high RPM features without the black box. What are those?
Charles