So I did a quick search and I have been having a hell of a time finding a diagram that matches my car... And that's the main issue I have. I just bought this car on Friday.

I believe someone removed the EGR so I'm not sure how my vacuum system should lock, and i'm also not sure what all the lines go to. The diagrams I find list colors but it appears that many of the lines have been switched with newer lines.

Anyway, my issue is that the car revs really high before it tries to shift, but when it shifts it feels like a normal shift. No grinding noises or stuttering or anything. The fluid is good and up to proper levels (I checked earlier today just to be sure) The previous owner told me that he kind of winged it when it came to the vacuum system, he didn't have a diagram and there's not one on the car I already checked.. The problem is the car he based it off of I believe is a 85 300TD... I'm not sure how much the routing changed but I think enough to cause issues.

Link to album: https://imgur.com/a/hgPeL4v

I'll try drawing a diagram showing how everything is routed tomorrow, looking at the photos I realize that is likely the easiest way to understand how things are routed at the current time.

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1981 Mercedes 240D - Automatic transmission

FYI, please upload pics to our server, because image hosting sites eventually drop them, or lock them up requiring fees... etc.

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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

Thanks for the information vstech! I'll do that in the future. I found a couple vacuum diagrams that I'm going to try this week (I'm working all week so time is tight) none of them look exactly like mine so I think some things including the egr are removed, which makes it a little difficult.

When went and tried to go through it on my old 240D, I found that the EGR valve didn't work (probably for a long time) and the stainless nuts and bolts holding it in had galled into one piece of metal. As long as their an EGR diagram on the sticker on the sheet metal under the hood and near the radiator and the vacuum routing seems to match it for inspection, just ahh. Well, you don't buy one of these because of the low emissions, except for C02 at least. At least check the EGR valve before going through some trouble.

To make sense of it, as I remember my federalized euro 82. It was probably imported in '85, as that's the only way NY would registers it, as an '85.

There was a mess of levers that operated a butterfly over the mouth of the intake manifold that was closed until maybe 80 or 90% throttle when it opened. This was to make manifold vacuum. The smooth operation of this complex mechanism was a testament to centuries of german clockmaking tradition.

There were 3 or 4 vacuum hoses and a push rod that went to a plastic box on the valve cover. One or two went to the thermostat housing, the other to vacuum supply. Another to the EGR valve.
If you opened it up, there was a rubber hose that got pinched off at full throttle.

I think the basic system operation was:
Wide open throttle disables EGR.
The EGR valve opens when the motor is warmed up.
The butterfly creates manifold vacuum so that the manifold sucks in the exhaust gas when the EGR valve opens.

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CC: NSA

All things are burning, know this and be released.

82 Benz 240 D, Kuan Yin
12 Ford Escape 4wd

You're four times

It's hard to

more likely to

concentrate on

have an accident

two things

when you're on

at the same time.

a cell phone.

www.kiva.org It's not like there's anything wrong with feeling good, is there?

Well I traced some of the lines. The vacuum line to the transmission wasn't hooked up at all. Does anyone know how I can hook the line? I'm not sure about the routing or where it's supposed to hook up exactly. I know there's a vacuum modulator but I'm not sure where on the transmission.

Also thank you for the run down on how the Egr works! It appears my car just simply does not have one however. I don't believe it came factory without one but rather it was modified.

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1981 Mercedes 240D - Automatic transmission

I do not know the 240D but I have a 1981 300SD. The vac modulator on the tranny is round and has a ridge in the center so you can turn it CW or CCW to adjust the shift. A vac line runs from the vac modulator (there is a nipple) to the VCV (vacuum control valve) up front at the injection pump. In the pic below the VCV is the white plastic gizmo with vac lines attached. It is supposed to supply about 10-15 ihg vac to the vac modulator until you hit the accelerator at which time the vac goes quickly to zero so you get a smooth upshift. For downshift it applies vac through the modulator to give a smooth downshift.

For the 240D I am guessing you have the same setup. So run the vac line from the VCV back to the vac modulator. Without you will get really bad upshifts, jarring. But the downshifts should be OK without it.

Subscribed .

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-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

Thank you! I wasn't sure if the vacuum line went to a junction between the VCV and modulator or not. The line was running down to the passenger side. I'm going to see if I can find the modulator and get everything hooked up properly.

Should there be anything else hooked up to the VCV? at the current moment I have a Y junction, one side goes to the transmission the other leads to a four way split that provides vacuum for all my internals. If I understand correctly that is wrong, and instead the internals should be connected directly to the switch over valve but I want to make sure. I do not seem to have a EGR on this engine, I do not know if the engine is older or if perhaps the EGR was just removed.

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1981 Mercedes 240D - Automatic transmission

I do not quite remember now and the diesel is in the garage. Will try to look tomorrow after Habitat. In general the vac goes through the VCV and then to the vac modulator. But it does Y a couple of times before the VCV. Again this is for a 300SD do I am not sure that your vac lines will be exactly like mine.

At this point you will be better off just putting a golf tee in the lines that go the the EGR. I will take a look at mine. That is what I did about two years ago and saw no ill effect.



More tomorrow with luck.

Thank you! For some reason mine has the junctions AFTER the VCV, not before. So I think something is wrong with my system... But more importantly.. I can't seem to locate the transmission modulator. I found where it's SUPPOSED to be but there's... Something there instead. Some weird plug, maybe a electrical plug? Is it possible it's on the passenger side? the transmission is filthy and i'm not sure where the vin for the transmission is, so I can't figure out the exact model.. In the morning i'll have to crawl under again and see if I can scrape off enough gunk to find some sort of numbers...


this is the plug i'm referring to. It's right in front of the shift linkage, where logically the modulator should be...

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1981 Mercedes 240D - Automatic transmission

No image.

I'm having issues getting it to work, I don't know whats up. The forum server won't let me upload to it and imgur is being a pain as well.

edit: got it sorted. For some reason my phone took the picture at a resolution of 4000 pixels... I didn't even think my phone was capable of those dimensions.

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1981 Mercedes 240D - Automatic transmission

Yes, the vacuum modulator is on the right side of the tranny, the neutral safety switch is on the left side in front of the linkage .

Put the right two wheels up on the curb and get into some old worthless clothes, the cleaning job you need to do is nasty to say the least .

If you have a trolly jack, jack the entire front end up and use safety stands, WORK SAFELY ! .

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-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

Thank you! I've been seeing transmissions where the modulator is in front of the shift linkage. pulling the right side up onto the curb is actually a pretty good idea, I can squeeze under the car pretty well without having to jack it up though, but raising it will help. I may end up buying some jack stands though just to make it easier. I'll update you guys tomorrow!

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1981 Mercedes 240D - Automatic transmission

This car weighs over 3,000 POUNDS so if it slips off the curbstone, jack or whatever, YOU WILL DIE .

I'm an old Field Mechanic so I have a lot of experience making access to under vehicle parts, you can dig a trench, or use a curb, if you use the curb be SURE the entire tread is on the curb ! none hanging over ! .

Find a place that has older, higher curbs and maybe a driveway drop apron to make it simple to drive two wheels up .

Expect to get *really* filthy !~ like Pig Pen in the old Peanuts cartoons .

It's O.K., this is part & parcel of mechanicing .

Wear eye protection ! .

Take some pictures, the folks here love the DIY photos .

Me, I get a lot of really grimy & greasy old vehicles so I have a dedicated pair of coveralls that button right up to my chin and fit snugly, I only wear boxers & a tank top under the coveralls, plus a cloth skull cap when I'm cleaning the undercarriage ~ I also work on a good piece of Concrete and use 3 ton safety stands and shake the car well before I go underneath it .

Then I can relax and use my cleaners, soft bristle brushes , rags and so on....

Keeping it clean makes the repair jobs so much easier .

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-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better