Herring,
No, actually the restricted orifice causes your modulator to receive a "weaker STATIC vacuum"... one that can more easily be modulated. Let me try to explain !

When I re-read the above parts of you last POST, I sense that I should explain my somewhat different way of thinking of vacuum control systems... a way that seems to help some better diagnose these systems.
Static Vacuum Systems - These are systems in/through which very little air actually moves except when the vacuum force momentarily actuates a diaphragm to perform some mechanical motion... door, fuel door, and trunk lock elements or "PODS". The vacuum modulator on the transmission is also an example... as is the EGR valve. IMHO orifices in a static only vacuum control system would accomplish very little!
Dynamic Vacuum Systems - These systems actually have air flowing through them either all or much of the time and the air flowing into and towards the vacuum source (our pump on the engine)... this provides the means to vary or "modulate" the strenght of the vacuum force in the system... or often thought of as " bleeding-off " the vacuum. For most of us the best example of this is the " bleeding " effect that the VCV introduces into our Tranny-Shifter Vacuum Control Systems. Your YR/model MB also has another dynamic vacuum component that is part of your EGR. Usually the "Dynamic" portion of a vacuum control system has a port that " Vents the vacuum " which is really backwards terminology... for the air actually enters into or through these "vents" which are usually terminated under the dash so as to better assure a cleaner source of air that otherwise (if in the engine compartment) would cause the system to clog up far more quickly. NOTE that the diagram for your car shows two such "vents"... both with an "a" label... one on the Shifter system's VCV and one on the EGR system's electric actuated switchover valve #81! Orifices I would think are primarily in and to my knowledge only in " dynamic " vacuum control systems.

Combo Static/Dynamic Systems - Yes, our Tranny-Shifter Vacuum Control System is a combination of multiple systems... the shifting part and the EGR part... and further it can be said that both of these systems have both static and dynamic components as I tried to explain above. The vacuum modulator that is physically on the transmission and the EGR valve itself are the static components... and the VCV and #81 electric Switchover Valve that is part of the EGR control system!

So let me now try to relate my thinking of how these two types of Vacuum Control Systems combine to give us proper transmission shifting. Let us first think of the vacuum modulator diaphragm that controls a hydraulic valve inside the transmission. As a " static " vacuum component, it it is "dumb" and IF it were connected up by itself as you tried, then its going to go to the fully actuated position and stay there... which would NOT help up much. These transmissions were designed to be hooked up to a gas engine with an intake manifold in which the vacuum level fluctuated wildely as the throttle and engine speed varies up/down. This is where our " dynamic " component (VCV) comes in for it's job is to translate the mechanical position of the throttle and use this to modulate the vacuum being sent to the Vacuum Modulator which in turn modulates the hydraulic valve inside the tranny.

So the VCV starts out NOT bleeding off any vacuum at all because it is shut out of the system by the switchover valve(s) that are also connected to the throttle linkages. When the VCV is first opened to the system, think of it as having a minimum " bleed " effect on the main vacuum (the power source) for the vacuum modulator on the tranny... but as you increase throttle, the mechanical linkage connected to the VCV causes an internal valve in the VCV to open more and more causing a greater and greater "bleed-off" of the vacuum being sent to the transmission vacuum modulator.

So the " main " or stronger vacuum is really that being initially sent to the modulator on the tranny... and it is the "dynamic" VCV component that is working as sort of a side-bar component to interpret throttle position and help modify or create a more appropriate vacuum signature being seen by the tranny vacuum modulator that thinks your car has a gas engine! This, IMHO, is why the German engineers devised the set of 6+ plastic orifices as a means to create what I think of as multiple vacuum pressure zones... and thus the need for the smaller size orifice in the line going to the tranny. Without this smaller opening, the vacuum being sent to the modulator would be too strong for VCV’s bleed-off effect to work (remember “dynamic” means there is air continuously flowing in there as long as the throttle is depressed). By using more than one orifice in your “combo vacuum system” allows the designers to create a strong initial 1st stage vacuum zone initially near the main vacuum line ( between pump and brake reservoir tank), and this is sent on via the switchover valves to power the EGR system… so the 2nd orifice is used to reduce the vacuum so that the VCV can properly modulate the vacuum signature. The VCV is adjustable but coming off the assembly line I’m sure that the orifices are far easier to use in making the final tuning of the vacuum level they want it to have.

So think about how air is flowing in these dynamic and/or combo vacuum control systems and you should be able to more readily diagnose problems! Oh yes, dirty orifices is why we put cheap in-line paper fuel filters on these vacuum vents or inlet openings under the dash! Once you get things working the way you want, then you put on these filters.
Regards... out of here!

Ok, so much to learn. I am going away but will get back to this next week, measure the vacuum going into the trans, and report what I find. It's really not as smooth as I'd like.

__________________
1982 240D automatic
Odometer quit at 307K...about 325K now

I'm back. Measured the vacuum today. The green 0.8 mm orifice is really not doing the job. Vacuum readings going into the trans are:
Idle: 10.5-11
"Gentle" acceleration: 2-4
Floored: actually goes slightly beyond where it goes when not hooked up to anything. Is it possible to get positive pressure in there somehow (I'd say +1 to +2). It's still within the "zero" zone on the gauge, though.

A couple of weeks ago I was at the salvage yard and pulled a thing off a W123 gasser. It's the blue-and-black thing on the line leading to the VCV in the attached pic. I know I need some more vacuum so I stuck it in the line. I noticed that it vibrates slightly when the vacuum is flowing through it.

This had the effect of boosting vacuum levels by about 2. That is:
Idle: 13
Gentle acceleration: 5
Floored: 1

I notice that when I suddenly let off the accelerator, the vacuum builds more gradually (takes a second or two to get back to 13 instead of building instantly).

So, I think this thing was worth the 50 cents I paid for it. However, it still leaves me with the same situation: more vacuum means that all shifts are softer. That's good for 1-2 and 2-3, which were too harsh and are now better. But 3-4 is now too soft and flares a bit.

Do you think there's some adjustment that can be made with the VCV, or is it a sign that the transmission's going to need to get opened up at some point? Is there a chance that the 3-4 flare can be repaired by replacing a spring inside the trans? I seem to remember something about replacing a spring on here somewhere a long time ago.
If not, should I just drive it with the flare until it turns into slipping (is that what'll happen next?) or should I look at getting a rebuild done now?

I am kind of bummed about this.

Attached Thumbnails

 

__________________
1982 240D automatic
Odometer quit at 307K...about 325K now

Herring,
I went back and looked at your previous POSTS and did NOT find where you took and/or reported what the vacuum reading is directly on the main/large vacuum line that goes from the vacuum pump to the power brake booster reservoir? I'm hoping that it is 15 or more inches of Hg. Take this reading by disconnecting the line going to your tranny shifter/EGR system and connect your hand pump/gauge to this same connection. Get the reading at idle... and they see how much it rises when you race the engine in short bursts. While you are there, spray some WD40 or such into the "T" connection where it takes off to the tranny shifter/EGR system... this to make sure this restricted orifice is not clogged! Softening up whatever might be inside the "T" should allow it to be sucked out by the vacuum pump! Also, after spraying things with the WD40, take a small diameter needle and poke it down into the opening while your are running the engine to help loosen whatever MIGHT be in there!

IF you have a much stronger vacuum reading there than what you have been are seeing at idle on the line leading down to the tranny's vacuum modulator and we are assured that you don't have leaks that are causing this... well then we can talk about adjusting the VCV which could be bleeding off the vacuum too much and needs to be reset/adjusted.

Do this and report back!
Regards,

Sam and Herring,
Sam, Good advice and the numbers will tell a lot.

I'm a little confused. Several months ago, I read all the posts in this thread and finished with the conclusion that the idle vacuum should be less than 10" in the transmission line. That would suggest the adjustment Herring needs should be to produce less, not more, vacuum at idle. Mine is now shifting a good as when it was new and my idle vacuum is 8-9 and bleeds off quickly to 0 under acceleration. Did I miss something?

__________________
Charles
1983 300D, bought new, 215k+ miles, donated to Purple Hearts veterans charity but I have parts for sale: http://www.peachparts.com/shopforum/mercedes-benz-cars-sale/296386-fs-1-owner-83-mb-300d-turbo-rebuild-parts.html

Ok, just connected the vacuum gauge/pump directly off (i.e. using a new Y-connector) the connection from the large diameter line. Readings are:
Idle: 13.5
Gentle acceleration: 6
Floored: 1


Or in other words, basically the same as I measured at the line to the transmission. Note that the orifice and the additional restrictor (blue doohickey in the photo above) only restrict the flow to the VCV. The line to the trans is a straight shot.

__________________
1982 240D automatic
Odometer quit at 307K...about 325K now

This might well be the ideal case. The story goes:

This car had always been a bit abrupt on 1-2 and 2-3, and "normal" on 3-4 since I bought it in January. Round about May, the 3-4 shift started to get slower. It was in the garage anyway for no glow light. I'd measured the plugs' resistance and found 2 bad and 2 good, and left the mechanic a note about that. When I called, I was told he'd replaced all 4 plugs. I guess there was a bit of annoyance in my voice or something when I told him to take a look at the trans.

I picked it up on a Saturday (no mechanic around) and I guess he'd spent an hour (what I was billed for) adjusting the modulator to its "hardest" setting. Now it revved way too high in gears 1 and 2 and slammed the shifts. But 3-4 was pretty normal. I called back on Monday and they said it was all they could do. The implication I got was that I was a cheap bastard and I guess they thought I'd have fun with my "fixed" car.

So, by adding the smaller orifice and restrictor to the VCV, I'm basically compensating for the "aggressively-adjusted" modulator. What I should really do is get down underneath and adjust it back, but I'd rather actually improve things first.

So, in one sentence, yes, my vacuum might be a bit "too high" but there's a reason for it, and fixing the reason won't fix my trans problem.

__________________
1982 240D automatic
Odometer quit at 307K...about 325K now

Thanks to both Herring's and Charles' [Cr from Texas], I have had to refresh my memory and thinking on this subject... and actually had to do some homework.

Yes, a new vacuum pump can generate well over 20" of Hg. vacuum... keeping in mind that when we say "vacuum" we are really talking about any absolute pressure that is less than atmospheric... which is typically ~30" at sea level. IF you read the MBZ manual section on these pumps, you will see that the Germans devised a way for you to quantify both level and the strength of the vacuum being generated by the pump. If anyone is interested in reading such, I can send you the PDF file!

As to what is the proper level at idle, the MBZ manual does not really address this... but I now think this is going to be basically a function of several things:
(a) just how new and/or effective your vacuum pump still is,
(b) how many leaks you have in any of the systems using this pump as a vacuum source, and
(c) the adjustment and condition of the vacuum control valve [VCV].

So how do you know what the proper vacuum should be at idle being supplied to your "Auto Tranny-Shifter Control System"... before you apply throttle. Well my current belief is that you want this to be the maximum vacuum reading that still allows you to reach zero at full throttle while driving down the road in fourth gear. IF you are NOT able to get it down to zero, then you need to either:
(1) make the restriction smaller or
(2) adjust the VCV so that it bleeds off more vacuum... AND
in most cases it's a lot easier to use the orifices.
Or you can do as "yellit" did... install the smallest brass icemaker control valve he could find in this line to allow him to effectively adjust the amount of restriction. I still want to try this so I can more easily experiment more on this subject, but I want something less than the 1/4 inch ice-maker plumbing valves... and I want one that uses a metal-on-metal "needle" type valve rather than the typical rubber-tipped valves that press against a valve seat!

Then I will be able to more easily test my hypothisis [sp? <--- professor Charles]... first with a long, large diameter, vacuum supply line run from and back to the engine compartment with the restriction-valve in it. I say "large diameter" for you see a long line that was too small would itself introduce friction losses and thus effectively become a part of the restriction but would be lost when you removed it from hanging out the window!

I hope these thoughts are of interest to you herring... and to others who read this THREAD!
Regards,

I downloaded a long list of things to check from a site that was posted earlier in this thread (I'll post the address, I left the list out in the car...something with mbz in the address).

First step was vacuum pump. I connected the mityvac directly to the orifice off the main (large-diameter) vacuum hose, with nothing else attached to that orifice. I got 20.5", which is about their spec (21"-23") so I think I'm good there. I tried putting vacuum into the system with the engine off. A squeeze would get it up to somewhere around 5" and that would bleed off fairly quickly (2 seconds or so), hope that's normal.

I'll begin going down their long list of things to do. Again, my frustration is that the 1-2 and 2-3 shifts are pretty much fine (or a tad harsh if I want to be picky) , while the 3-4 shift is kind of slow/mushy. Reducing the restriction further improves 1-2 and 2-3 and worsens 3-4 so "more vacuum" isn't the answer I'm looking for. Sometimes I wonder if I've set my expectations too high for a car of this age, but people claim to be able to get theirs silky-smooth in all 3 shifts so I want to achieve that or become convinced that it's not possible on mine. No one's indicated that subpar shifting is a result of mechanical wear inside the trans, which propels the car forward just fine once it's in gear, so I'll keep going with the hope that it's a vacuum issue.

And yes, Samuel, I do really appreciate your input on all of this.

__________________
1982 240D automatic
Odometer quit at 307K...about 325K now

Herring ,
Earlier you POSTed:
These pressure drops you reported struck me as od unless the tranny-shifter control system was connected via the “Y-connector” you used!?
------------------------------------------
------------------------------------------
Now at (A) above, you reported 21-23 inches (of Hg) vacuum readings on your 1982 240D… and this tells me that it appears that your other vacuum using components/systems are reasonably tight and not leaking badly. My 240D starts out with about 20” and the needle vibrating… and as you increase throttle, the needle steadies and rises just slightly. Even so, as hopefully you continue to try and make further improvements in your Tranny-Shftr.Vac.CtrlSys [aka = T-SVCS]. I would suggest that while parked and doing this work that you use golf tees or other means to disconnect and plug/cap-off these other vacuum systems [but NOT the power brake booster reservoir]. Report back any differences you see reading the vacuum directly and only off one of the Tee connections on the large, main, vacuum line.

At (B) above, I think you are saying that you tried to use your hand pump/gauge to see IF you could manually pump down the T-SVCS !? Personally I commend you for your inquisitive interest… but since this system is a combination of both “dynamic” as well static components, this will not show you much. The Vac.Ctrl.Valv [VCV] works by allowing air to enter the T-SVCS and thus the vacuum loss and the confusing term “bleeding”. Normally this term is used when referring to “bleeding off” air pressure stored inside something… but in this instance always remember that these VCV(s) are air to enter the T-SVCS… try to think of this air traveling along the lines and thus reducing the level of vacuum on the other side of the VCV that “TeeD” into the line going down to the TrannyCtr.lModulator [TCM]. This “dynamic” side of this T-SVCS system makes hand vacuum pump evacuation pretty much impractical ! The vacuum pump is mostly to test static vacuum components… EGR(s), TCM(s) Door-Lock Elements [aka “PODs”] etc. Yes you can use the hand vacuum pump to test the tightness of sections of the T-SVCS dynamic system when the engine is shut down… and you can monitor the vacuum level of the T-SVCS system while the engine is running, but the hand pump is pretty much for static components with no air flowing though them!

At (C ) above I’m not sure what you list you are referring to but yes, get the link address and I’ll take a look!

In closing let me try a step-by-step approach to your troubleshooting efforts… and that means more Q(s):

[1] Isolate the vacuum systems... such that only the Brake Booster is connected to the large, main, vacuum line.

Q1 – What vacuum readings do you see at one of the T(s) coming off the large, main, vacuum line?-------------------------------------
[2] NEXT connect the T-SVCS to the main vacuum line via one of the T(s) … then plug and/or Cap off the connection between the T-SVCS and the VCV for we want to see IF you can hand pump down a measurable vacuum in the remaining STATIC components and lines of the system.

Q2 – Are you able to do [2] and does the vacuum hold?

Let’s NOT get too far along with this step-by-step approach… and these were mostly to test the STATIC side of the T-SVCS system.
Soon, maybe even next we will add in and delve into the dynamic [VCV] part of the system.
Sam

A: at idle, if I have the transmission connected to the vacuum line, and test the vacuum near the large-diameter line via a Y-connector, I get 13.5". If I disconnect the transmission and plug the mityvac directly into the large-diameter line, I get 20.5".

B: If I leave the mityvac plugged directly into the large-diameter line and turn the engine off, vacuum drops steadily to near-zero fairly quickly (less than 5 seconds). If I then use the mityvac to pump vacuum into (from) the system, it falls off quickly. So, my conclusion is that the system is designed to hold only a small (but slightly greater than zero) amount of vacuum when the pump is not operating.

C. Ok, I will try vacuum-pumping the VCV/trans side of things when I next get to work on the car.

__________________
1982 240D automatic
Odometer quit at 307K...about 325K now

OK Herring... let me revise my instructions for [2] above... and to NOT connect the T-SVCS to the main vacuum line for you will connect your hand vacuum pump to the T-SVCS as modified by the remainder of my instructions in [2] above! Be sure to … plug and/or Cap off the connection between the T-SVCS and the VCV... for we want to see IF you can hand pump down a measurable vacuum in the remaining STATIC components and lines of the system.

I hope my responses as done above, interspersed inside your previous quotes makes it easier to follow in this THREAD!??

Maybe some day we can do this with streaming, live, video!
Regards,

Very strange issue today. Drove the car for the first time in 6 days. When I first accelerated, I thought the trans was suddenly starting to slip. Acceleration seemed slow, and the 3-4 shift was very flare-y.

Fortunately I had my mityvac in the car and hooked it up on the way home. The "slipping" was just the 1-2 shift, happening immediately on me tapping the gas. The reason why is my vacuum has suddenly soared.

Vacuum on the transmission line is now 16.5 at idle and 10 floored. This is from 13.5 at idle and 1 floored. I took off the blue thing (pictured in post 483) I'd put in the line to the VCV and vacuum fell to 14 idle/9 floored.

What on earth can cause a sudden, huge shift in vacuum like that? Particularly the fact that vacuum is barely falling under acceleration? Did my VCV just croak?

__________________
1982 240D automatic
Odometer quit at 307K...about 325K now

Herring,
Sincerely, it's difficult enough to diagnose problems with these systems "remotely" based upon another's observations! I'm afraid that your introduction of parts from a "gasser" might just make some of us become reluctant to try and help you further! For me personally, I'm inclined to say remove any and all such "gasser" or other parts that are NOT OEM to your model... and lets take inventory of just what your systems looks like. I will be glad to help you further IF you agree to do this... and will take the inventory you tell and/or show me with any photos and graphically edit a vacuum diagram and post the diagram where it will be available 24/7 elsewhere [NOT on this FORUM]. This way we will not be restricted by the 65K file size limit. Given such a diagram as a reference that I can rely upon I think we can work through your symptoms and give you good advice.

We need rules or we will be spinning our wheels bouncing vagaries off each other for ever. I for one need clarity as to just what your car's system has on it ! So IF my memory serves me well, your's is a 1982 240D... so IF this is correct, I suggest that we start with the diagram at: http://www.peterschmidtransmission.com/vacuum/1977_1985/616_617_91/616_617_91.jpg . Take this diagram and describe exactly what you have actually connected up on your car's "Auto Tranny-Shifter Vacuum Control System on yur car. You can do this OFF-Line by sending me an email [direct please... NOT this FORUM's email system] and I'll start editing the diagram using color and we will then have clarity as to what we are talking about ! Again, I am prepared to post this where we can open the diagram in a separate window and follow along with what the other is saying in their POST. To get the ball rolling you can also give me your telephone numbers and I can call you using my unlimited internet VOIP telephone line and we can chat to give me the information I need to edit the diagram. Sorry I didn't see this coming and establish "rules" sooner!

Regards,

I have an 83 240D with tranny problems, I believe it is the vacum system. I think I have narrowed it down to the White Bleed Valve on back of Injector Pump but I can not find it any suggestions greatly appreciated. Maybe I have the wrong name.

Thanks GM