W123 Vacuum Progress….

[dot]

Hi All,

I’m making some progress with the ‘85 300TD, although still having some electrics issues I’ve put on another post in the appropriate section.

My replacement rear passenger door actuator arrived today and was duly tested and fitted. Works a treat. I worked around the rest of the doors and then found on the passenger side that a red vacuum line was wrongly connected to the green line. Rectified that.

So I then with some trepidation thought I may then get an engine shutdown and a working central locking system. Nope.

When I isolated the locking system with the vacuum pump it locks and unlocks perfectly. And with everything connected back up the engine shut off valve ALMOST works. So I’ve turned my attention to the engine bay.

The shut off valve definitely holds vacuum. The line from that to the 4-way connector is good.

The main brake servo vacuum line is good.

The line to headlamp adjuster seems to let by a little. I will change this. Lines to headlamps ok.

So this brings me to the gearbox. I can’t achieve any vacuum from any pipes, and the green check valve appears to let by both ways. That can’t be right can it? And in the photo the bottom line (circled) attached to the side there just goes to open air? I can’t find anything about this except for one post somewhere that says it is supposed to go to open air?

Any gearbox vacuum advice appreciated - my last q is would this stop the engine shutting down? I literally have to just touch the manual shut off lever and the engine switches off, so I’m almost there!

Thanks all, Dot

 

[optimusprime]

Any vacuum leak in the system will cause the engine to run on after you shut it off . Have you got a w/s/ manual on the W123 ?

 

[dot]

Any vacuum leak in the system will cause the engine to run on after you shut it off . Have you got a w/s/ manual on the W123 ?

Aye - find it awkward to follow that’s all

 

[optimusprime]

So a little vacuum is being lost from one pipe or another .Use the forum search at top of the page and in it put -
85 300d w123 vacuum ?s with video . --- -- the video wont work but check info vacuum the same for tutbo

 

[grober]

Mercedes-Benz OM601 engine - Wikipedia

en.wikipedia.org

 

[Petrol Pete]

This perhaps ?

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[Stratman]

A good job I read to the end of the thread, I was about to suggest smoke testing the system

 

[Bellow]

Ditto - with a fag.

 

[dot]

This perhaps ?

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Just bought one…

But a q - is the green valve pictured here a one way thing as I’m getting blow through both ways?

And what’s the bottom right angled line with the green stripes for - this is open ended over in the other side of the engine bay??

 

[grober]

603 Diesel Engine Vacuum Hose Leaks and Faulty Routing | Vacuum Problem | MercedesSource.com

mercedessource Tech help - If the hoses are leaking or are not hooked up properly a number of problems could occur. The following images are posted to help those working on the engine control vacuum systems for the early 603 engines. These include the 1986 to 1987 300SDL and the 1987 300D and...

mercedessource.com

 

[DITTRICH]

By the time you get this fully sorted, it will be MOT and VED free. A present to look forward to

 

[dot]

If that’s this week then bring it on! FInally there with electrics, I’ll do a detailed post later.

Got a smoke tester to find that last leak on the vacuum system. The engine is trying to shut off (much much better than it was, so it must be almost sorted).

Got Mot prep to do for tomorrow. Fingers crossed.

 

[dot]

Smoke tests revealed one leak, one of the vacuum pipes to the ignition barrel had come off. I then ran her up and down the road and upon my return the central locking now functioned fine, but the engine would still not shut down, so I turned to the shut off valve. When I shut down now the valve moves to literally a gnat’s dangly bits away from shutting down, suggesting to me (am I correct?) that the system is pretty good except for this one bit now? I’m going to change it anyway, but there doesn’t seem to be any UK sellers and Mercedes told me today they can’t get me one - any ideas anyone?

While this was all happening, it’s passed its MoT with one brake pipe advisory which I will change, so am pretty happy. My electrical gremlins were solved, but I’ll cover that in that section of the forum.

Got some freshly powder coated alloys and new boots, personal preference, but I like this look more than the steels/hubcaps. So off for a celebratory haircut and coffee

 

[Stratman]

I’m going to change it anyway, but there doesn’t seem to be any UK sellers and Mercedes told me today they can’t get me one - any ideas anyone?

Try a breaker. I'd guess, and a guess is all it is, that part would have been used across a number of vehicles so shouldn't be too hard to source second hand.

 

[Bellow]

I’m going to change it anyway, but there doesn’t seem to be any UK sellers and Mercedes told me today they can’t get me one - any ideas anyone?

Try a breaker. I'd guess, and a guess is all it is, that part would have been used across a number of vehicles so shouldn't be too hard to source second hand.

Probably more vans than cars with that diesel engine.

 

[G7Wagen]

Found this By chance..
(I am not the Author)

W123 Transmission Vacuum Diagram & Shift Issues
If your W123 diesel has shift issues, there is a very good chance that the transmission is just fine.

There are several things to check, and most of them are vacuum related. Any part of the vacuum system that is failing can and will cause disruption to the transmissions ability to shift properly

SYMPTOMS:

Transmission quickly progresses through gears (1-4) from a stop and does so a bit sloppily. Or perhaps there is flaring between particular shifts. Or perhaps, the transmission is not wanting to shift at all or shifts very late.

These symptoms should be checked at once to avoid potential damage to the transmission. The following check list will help determine what might be going wrong.

CHECK LIST:

Transmission Fluid: Drive car for at least 15 min. to make sure engine and transmission are at full operating temperature. Check fluid level with gear selector in "N". Do not use "P" as you will not get an accurate reading. NEVER OVER FILL the transmission.

Vacuum System: Must be in perfect working order. Even the smallest leak can cause havoc on how the transmission shifts. If need be, isolate the leaking sections by disconnecting them and capping off at the location. Remember, if the vacuum is to high the transmission will want to shift to quickly, if the vacuum is to low, the transmission will not want to shift at all. The transmission vacuum system for the Mercedes 240D is as follows:



The VCV and Transmission vacuum modulator are no longer available from Mercedes-Benz.

Main Vacuum Circuit Components

Change over valve (located on top of valve cover) This part breaks regularly!
Vacuum control valve (VCV)
Vacuum modulator (located at side of transmission)
Vacuum Dashpot (check valve) green in color

ADJUSTMENTS:

If your transmission fluid is at a proper level the next step is to ensure your vacuum system is in perfect working order along with the throttle linkage being properly adjusted

Once you are sure the fluid, vacuum and linkage are in good working order, the next step is to adjust the VCV valve.

HOW TO ADJUST THE VAVLE:

1. Loosen the VCV valve retaining bolts (no need to remove)



2. Remove side cover



3. Using a wrench, turn the nut on the end of the spring counter clockwise if your transmission is shifting early and clockwise if shifting late. NOTE: To make this adjustment you MUST hold the throttle linkage in the closed position while turning the nut. It is also important NOT turn the the adjusting nut more than a few millimeters at a time. If you over adjust, your transmission will not shift out of first gear.

Leave the cover off while test-driving the car to make it easier to make adjustments while you are on the road.

If this adjustment still leaves your transmission shifting a bit late or early the next step is to adjust the transmission vacuum modulator which we will cover in a subsequent article.

 

[G7Wagen]

and this

 

[G7Wagen]

123 wiring diagrams

 

[G7Wagen]

Interesting article.

W123 Diesel • Rough Idle
If you have come this far, you either own a W123 diesel or are interested in acquiring one. In either case, there is no need to settle for a rough running diesel Mercedes.
If you have a W123 diesel, 4 or 5 cylinder, there is no doubt they vibrate and are certainly louder than modern diesels, but that is no reason not to make sure your Mercedes is not running as smoothly as possible.

When I acquired my 1981 240D, and not being familiar with just how these diesels were to perform, I was more forgiving than I am now. Regardless, the following are a few very important items to look at and know about.

Let's work from back to front to find out why it might be running rough.

• Is the fuel tank filter clean or new? If you don't know it's time to find out and most likely replace it.

• Are the rubber connecting lines from the fuel tank filter and along the way up to the front of the car new? If not they are most likely brittle and can easily be drawing air into the system. Even if they are not leaking they can be allowing air in.

• The two fuel filters, primary and secondary, in the engine bay also need to be changed at specified intervals.

• Check the plastic fuel lines that are probably no longer clear but dark brown. These too can become brittle over time and begin to allow air into the system.

• The primer plunger must also be checked. If you still have the all metal unit it is most likely leaking and should be changed for the the newer Bosch unit. If you have the newer plunger, depress it 6 or so times and see if it leaks around the base of the plunger. If it does, you are drawing air into the system from there.



Another important factor are the injectors. How long has it been since they were rebuilt or replaced? Again, if you don't know it is time to pull those and have them tested, and if need be rebuilt. Also make sure they are not leaking. If they are, air will be introduced into the system at that point as well.

• Check the air filter!

• Make sure all the hard injector lines are tight at the pump and injectors. Do not over tighten!



Once all these items have been checked and or replaced, you should notice a major difference in performance and smoothness of operation. I also recommend running a lubricant/cetane booster in every tank. With the growing distribution of low sulfur and ultra low sulfur (LSD/ULSD) diesels, the older pumps are not sufficiently lubricated and require additives to reduce excessive wear.

I would recommend Red Line 85 Plus Diesel Fuel Additive. This also keeps the engine running much smoother and appears to provide a touch more pep. Every little bit helps. If you are not running additives in every tank to help keep water and sludge from clogging up the system, your entire system might be in need of a good cleaning as well. A very good cleaner I use every 6 months is Liqui Moly Diesel Purge.

It should be noted, that there are many other factors that can cause rough idle such as poor compression, worn timing chain and injection pump timing.

 

[G7Wagen]

Hope these are of some help with your 123