Following that link doesn't work for me.

Ok, back from vacation, haven't gotten a vacuum gauge yet but printed out this vacuum diagram and looked under my hood:
http://home.comcast.net/~phantoms/vacuum/fuel_egr_240d_auto.jpg

On the diagram, looking at part 71, lines 1, 4 and 5 are disconnected...short pieces of line are attached that are not attached to anything at the other end.

Part 72, the green cylinder on top of the vacuum control valve, is NOT attached to line 5 from the central plug but rather to a line coming straight from what I assume is the vacuum pump (Haynes manual basically ignores the vacuum system). I have no colored orifice (63) at all.

It appears the point of these mods was to bypass the switchover valve (64).

So:
1. What is the function of the switchover valve? Is it common for this to fail and be bypassed? The Brotherton article states that this is to prevent overboost but 240Ds don't have a turbo. It also says that "the valve is often sooted closed"--should I try blowing it out with a can of compressed air?
2. Should I try just reattaching lines as in the diagram and see what happens? What color orifice should I get?
3. The Brotherton article says to attach the vacuum gauge at the "case pressure port"--where's that?

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

======================================================
Let me first try to answer your Q1(a) above with this far too long answer... and first trace the vacuum from it's source down to the switchover valve:

[1] The main Vacuum source is the engine driven pump (#67)…
[2] The bulk of this vacuum is for the vacuum assist power brake system…
[3] Thus orifice #62 acts as a restrictor to prevent loss of braking power in event of a complete rupture of the vacuum shifter control system...
[4] After passing through orifice #62, this higher strength vacuum [vac#62] splits at the “ T ” connector…
[5] One branch passes through orifice restrictor #63 to further reduce the vacuum [vac#63] before it goes via the " Y " connector on to port #4 of the Mech.Switchover Valve ( #64/64a [" MSOV "] ) as well as goes on to the tranny vacuum modulator via “ b ”…
[6] The other branch of vac#62 goes on to port #1 of the MSOV…
[7] The VCV (#65) connects via the surge damper (#72) and then to port #5 on the MSOV…
[8] The vent side of the VCV splits and in addition to venting under the dash, it also connects to port #2 of the MSOV…
[9] and to round things out, the EGR system is connected to the MSOV via port #3.

Finally an answer to your Q1(a)...What does the MSOV do?

In short it does mostly the same thing the much simpler 2x3 vacuum valve on our earlier 1980 models does... so take a look at this much more obvious system at: http://www.peterschmidtransmission.com/vacuum/1980/617_912.jpg

So now for what the MSOV does:

[A] The MSOV is actuated by movement of the throttle and at idle closes off the VCV from being connected to (via port #4 ) and thus bleeding off vac#63 being sent to the tranny’s vacuum modulator valve…
[B] As you open the throttle, ports #4 & #5 are opened to each other and allows the VCV to begin bleeding off vac#63 that is being fed to the tranny’s vacuum modulator.
[C] Similar to [A] and [B] above but separately, the MSOV also acts as a switch for the high vac#62 to be fed to the EGR system via ports #1 and #3… and I speculate that this too is closed off at idle and opened as you increase throttle. You might even find that it closes off at some position of high throttle. I would guess that you could ascertain this by using your vacuum pump or just blowing air through port #3 and see if it comes out at port #1 as you manually simulate throttle changes by moving the MSOV linkage!
[D] The one thing I canNOT tell you for certain is why port #2 on the MSOV feeds back to the vent side of the VCV. You are on your own regarding this port and what it’s function is !??

[E] Otherwise this MSOV mostly adds the additional sophistication to how the EGR system functions… just as the electric switchover valve (#81) does. In later models, especially on the infamous “California cars”, they went hog-wild, adding 5+ additional components mostly in an attempt to reduce the engine’s pollutants!

Answer to Q1(b) - I think it's common to find failures in this double vacuum switching arrangement and the fact that both vacuum switches are encased in the same housing probable causes more confusion and thus people abandoning these functions that are only adding small improvements in performance. The Brotherton article can be confusing because I suspect he wrote the article [out of necessity] trying to make it applicable to as many cars as practicable!

Answer to Q2(a) - I would first do some "puffing" and verify that I am correct about the 5 numbered ports on the MSOV and see IF you can figure out port #2 which appears to be a vent function... and once you feel you understand how it is suppose to function... I would try to repair it to function OEM... with one possible exception... the EGR system which I would disconnect and plug up unless your state does smog inspections on these cars!

Answer to Q2(b) - I have found very few MBZ diagrams that show the actual color code for these restricted orifices... and for me I found it easier to have a complete set of these somewhat cheap orifices on hand and to install them by trial and error! These serve as "fine-tuning" tools for the tranny shifter system and thus I could readily understand that identical cars coming off the assembly line might end up with different orifices!

Note... for me writing out something in such detail as in the above... this helps me to think out such systems and controls and I come away with a better understanding that IF I did NOT do this! Let me know IF you figure out what the line to MSOV port #2 is all about!

Thanks for the much clearer vacuum diagram for your car !
Regards,
Sam

Ok, sounds like I will be paying a visit to the dealer for some vacuum line, a y-connector (to make my vacuum tester) and a set of orifices. I really appreciate your help with this stuff. I couldn't own a car like this without the resources of this board.

Question: how exactly do I "plug up" the EGR system--what am I plugging, and what's the standard way of doing it? Is there a step-by-step anywhere?

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

One simple way is to make a solid "gasket" from a piece of sheet metal (even a Coke can will work) and place it in between the EGR valve and the intake manifold. That will retain the car's appearance while defeating the EGR function. The intake manifold will no longer see carbon-loaded exhaust and, if you remove and clean the intake, will stay clean.

Another simple way is to block the vacuum line to the EGR valve, thus preventing it from operating. Blocking the vacuum line is as simple as inserting a 'BB' in the rubber jumper that connects the plastic vacuum line to the metal nipple on the EGR valve.

Both of the above procedures are unobtrusive and might even pass an inspection. Caveat: my state does not inspect so you should get an opinion from forum members in states where inspections are performed.

A more extensive removal involves a kit that one of the forum members sells. It allows you to remove the EGR valve from the engine and cover the holes in the intake manifold and the exhaust pipe.

Finally, you can remove the vacuum valves from their place (usually on the left inner fender) in the engine bay and plug/remove the various vacuum and vent lines. It goes a long way towards cleaning up the look under the hood.

I recommend labeling all of the parts and pieces and documenting your work so that you can reverse it if it ever became necessary.

I don't know if there is a one-size-fits-all DIY since there are so many versions of the EGR system. There are many threads talking about EGR removal. I suggest searching for them and seeing what information and pictures are available.

Jeremy

__________________

"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970

Jeremy- I agree with your advice... especially IF exhaust is leaking through the EGR valve when NO vacuum is applied to it... but IF it is holding and NO exhaust gasses are coming through to the intake manifold... well then I recommend the following:

Herring - IF there is no exhaust-to-intake " leak-through ", then I would simply use golf tees and/or appropriate rubber caps on the vacuum source side of the EGR line... this to plug up the vacuum!

IF you have to be concerned about the vehicle ever being subject to a smog inspection in your state, you could use the "ol beebee instide the vacuum line trick" !! This way externally things visually look OEM!

Also at one time Brian Carlton put together a limited production kit [~$30] that allows you to remove the EGR valve and then blank off both exhaust and intake manifolds using bolt-on stainless steel [<--I think] flanges!

Finally, I think the easiest way to sort out the routing of the multiple ports [ #1 thru #5] on the mechanical switchover valve is with the engine off to just hook up a piece of clean hose to what I eariler ID'd [ports #4 & #1] as the two inlet ports [ shifter subsystem & EGR subsystem]... and the blow into these ports [one at a time] while your rotate the throttle... and look for where the air is coming out at another port. Once you know the port-to-port switiching arrangement, then you can test things with your hand vacuum pump and know more concretely which need repairs. I was able to get parts for my 2 1980 models [~$20] so hopefully you can do the same for your 1982. I believe you will find either one double vacuum valve or two single valves under the black cover!?
Regards,

Ok, I bought some vacuum line, some Y-adapters and a Mityvac. First, I attached the Mityvac and drove around. 11 inches of vacuum at idle, down to zero at full throttle. I thought that was odd, that's pretty much in-spec, and the way the trans drives is definitely not.

I had called the dealer for orifices and they told me they are all unavailable except for the largest (yellow, 2mm) and the smallest (green, 0.8mm). I bought one of each. (Kudos to Larry at Mercedes Benz of Fort Washington, PA for his patience with me and also for mailing me the orifices when they came in.) After pulling things apart, I noticed that my car DID already have a yellow orifice installed. So, I replaced it with the green one.

Shazam! Shift points are where they should be, shifting is smooth. I can't believe it, and all with a $4 part. It's like a whole new car. Thanks for everyone's help, even though this turned out to be simple I'd never have been able to tackle it (or even know the part number for the green orifice) without your help!

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

Herring,
I'd like for my very specifically titled THREAD to take credit for your $4 miracle... but the engineer in me is more than a bit skeptical of your miraculous result!

Let me speculate some…
(1) first off the 11 inches seems a bit low to me,
(2) you started out with what was probably a dirty 2mm orifice, and
(3) you replaced with a new 0.8mm orifice.

Something just does not quite jell here...

PLEASE measure and report back to us what the vacuum now is at idle and what it drops to when you put “the pedal to the metal” ?

Also... I think the full range of 6+ orifices are still available !

Proud originator of this THREAD,

I know it should be a tad bit higher. What specifically would I do to raise vacuum at idle?

I just compared the orifice from the car with the new 2mm orifice I bought. Other than one being a bit dirty, they're identical. That is, the old one does not appear to be constricted by dirt at all.

Keep in mind that the PO had cut out big chunks of the vacuum system. The vacuum goes directly from the supply line, through the spaceship and into the VCV.
That is, on this diagram:
http://home.comcast.net/%7Ephantoms/vacuum/fuel_egr_240d_auto.jpg
I replaced the orifice at 62 (yellow to green) and the line out of 62 is going directly into 72.

You can see in the attached picture what I'm talking about. The yellow stripe in the line just above the green spaceship is the old orifice.

Would all of this make any difference in the expected result of the replacement I made?

OK, will do.

Well, not according to the parts guy at the Benz dealer nearest me. I read him the list of part numbers (which I got here) and all but those come back as unavailable in the computer system.

Attached Thumbnails

 

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

The orifice is usually inserted in the Y connector. Did you also replace the Y?

Sam's point is very valid - what are the vacuum numbers now?

__________________
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

Herring... and Charles,
Yes, now your situation is beginning to make more sense... the 2mm larger orifice was originally necessary for it was supplying vacuum to both the Tranny-shifter system as well as the EGR system so more was needed then. But then I believe you said the EGR was disconnected... so this left too much vacuum and the double switchover valves were played with so the VCV was/is probably hooked up such that the VCV bleeds down the vacuum even at idle when normally the switchover valve would NOT be open to the VCV and allow it to bleed off the vacuum.

Assuming I am correct that you are no longer using the EGR, I would try to figure what ports connect to what other ports at idle and at higher throttle positions. What I'm getting at, is that I think you should try to restore the switchover valve or valves necessary to restore the switching ON/OFF of the bleeding action of the VCV. There are subtle reasons for this action that is based upon throttle position... e.g. possibly to prevent the car from down shifting too soon... or too late! So using the "puff/blow" method I described earlier, try to figure out basically which of the 5 ports connects are interconnected at idle and higher positions of throttle. I think you will find that #1 & #3 connect and that #2, #4, & #5 interconnect. You need to first confirm my speculation... and then work on restoring those that control the shifting [ #2,#4, & #5 I think]... making them vacuum tight. These switchover valves are not too expensive [ ~$20 to $30]. Then IF the vacuum level being sent to the tranny vacuum modulator is too high or low, then we can get into how best to adjust this... including adjusting the VCV!

Keep in mind that on our 1980 models, we have a simpler switchover configuration... especially when you take the EGR system out of the picture... these cars only have the one valve that simply turns ON/OFF the VCR bleeding action. Take a look at: http://www.peterschmidtransmission.com/vacuum/1980/617_912.jpg
We are working toward such a simpler system for you too IF I'm correct that you too have abandoned your EGR!??
Regards,

Ok, first I have to say I was a little overoptimistic on my "cure". While it certainly did help things, the 1-2 and 2-3 shifts are still not smooth. The best I can say is that if I accelerate "just so" I can get them to be smooth...which is an improvement. And they're always smoother than before.

To recap, I've got a line coming directly off a large-diameter trunk line, which goes through a "Y" connector. One branch goes to the VCV (through the flying saucer), the other goes to the transmission. Where the 2mm orifice was (and where the 0.8mm orifice is now) is past the "Y" going to the VCV. So this has the effect of "diverting" more vacuum to the transmission.

I played around a bit today, putting the orifice on the "input" side of the "Y" (reducing flow to both the VCV and the trans). It made things slightly worse. I then removed the orifice altogether and capped off the line to the VCV, so 100% of the vacuum went to the trans. Very smooth, but no power due to being always in too high a gear, and slow shifts. Stupid me left the Mityvac behind so I didn't measure vacuum but now I have a sense of what's going on. Ideally, the trans needs more vacuum than it gets now, but not all that the pump can put out. IOW, an even-smaller orifice (if such a thing existed) to the VCV would be ideal.

I will still probably work on restoring the flow to the switchover valves on top of the engine. I did the puff test today, as far as I could. Again referring to the above diagram, this is part # 71.

Air blown in hole 1 comes out hole 3.
Air blown in hole 5 comes out hole 4.

This is at idle.

Hole 2 on my vehicle is broken off at the connector and capped off with a bolt on the hose side. This could be the reason my system was so "hacked".

Question: If I don't want the EGR valve anyway, it seems like there wouldn't be any reason to restore the hole 1/3 flow (which just goes to the EGR valve). Am I right on this? So what else does the switchover valve do?

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

Mine is an 83 300D so it may be a little different. I got the best results by changing the Y connectors that go to and from the EGR with straight hose (preserving the orifices). That effectively removed the EGR and the black box valves from the system.

__________________
Charles
1983 300D, bought new, 215k+ miles, donated to Purple Hearts veterans charity but I have parts for sale: http://www.peachparts.com/shopforum/showthread.php?t=296386

Herring - I'm sorry but as much as I would like to follow along with your situation, I'm really having trouble and the thing that really frustrates me is that I know that IF you could take the vacuum diagram and edit it graphically as I would do [IF in your situation]... I know this block I'm having would NOT be there!!? IF you have the skills to edit "JPG" graphics files... especially using colors to show more closely how your Tranny-Shifter Vacuum control system has been modified and presently exists... please do so!! IF NOT, in the future, please refer to components by their number designation on the diagram!!

But in the mean time let me try to get some clarity with these Q(s):
(a) I think by large-diameter trunk line you are referring to the large vacuum line between the vacuum pump and the brake booster reservoir?
(b) Im just not surce as to what you are calling the flying saucer) !??

I'll let you chew on these 2 Q(s) and I'll come back in a separate POST to try and address the last part of your last POST!
Regards,

Herring - I'm sorry but as much as I would like to follow along with your situation, I'm really having trouble and the thing that really frustrates me is that I know that IF you could take the vacuum diagram and edit it graphically as I would do [IF in your situation]... I know this block I'm having would NOT be there!!? IF you have the skills to edit "JPG" graphics files... especially using colors to show more closely how your Tranny-Shifter Vacuum control system has been modified and presently exists... please do so!! IF NOT, in the future, please refer to components by their number designation on the diagram!!

But in the mean time let me try to get some clarity with these Q(s):
(a) I think by large-diameter trunk line you are referring to the large vacuum line between the vacuum pump and the brake booster reservoir?
(b) Im just not sure as to what you are calling the flying saucer) !??

I'll let you chew on these 2 Q(s) and I'll come back in a separate POST to try and address the last part of your last POST!
Regards,

Herring,
Switchover Valve ports #1 & #3:
So on the double mechanical "switchover valves" inside the black box that is controlled by linkage to the throttle [#64/#64a]... so I basically guessed correctly that at idle at least ports #1 & #3 interconnect and thus these provide a simple ON/OFF vacuum signal for the EGR system so it is OFF at idle. Just in case you decide to restore your EGR system to full operation, I'm thinking this vacuum signal might also be present at a higher throttle position!
Switchover Valve ports #4 & #5:
Once again it looks like I am at least partially correct. As to the #2 port, I admit that I must NOT claim to fully understand why there is such a feedback line from what I call the "bleeder" side of the VCV [#65]. My best speculation is that at certain throttle possitions, this line provides a moderate-to-strong vacuum via this line as a means to nullify the VCV's bleeding effect through the line that vents under the dash... and thus nullifies a tranny shift under certain load/throttle conditions.

The later models muddy my understanding of such " stuff " even further... and the 1985 CA cars also add another 5 components to the system that are in or related to and accomplish a much more precide tranny-shifter control and feel of luxury!

Your Question now:
Blocking OFF the EGR system - Yes, so long as the #1 & #3 ports are serving only the EGR system and as long as your STATE dose not arrest you and drag you off to jail for not having it hooked up, I would simplify things [at least for now] by putting golf tee(s) in the line that goes to #1 & #3 [just in case] and also the rubber "T-connector" that supplies vacuum to #1.

Closing Sidebar - On both our much simplier 1980 models, I have learned to use the throttle to help me control shifting... and have found with a little practice I can do quite well at this... basically by backing off on the throttle just enough to make for a smoother shift between:
(a) 1st & 2nd gear..................... by feel
(b) 2nd & 3rd............... @ just before 25 mph........... and
(c) 3rd & 4th............... @ ~30 mph and above !
I feel that doing this (1) minimizes wear on the tranny and (2) allows me to drive more for economy by keeping the RPMs down!
For economy, I'm even running 35 psi "all the way round" in the tires!
It's too soon to give a report on any favorable results!
Regards,