The issue I am chasing is not vacuum. I have disconnected the vacuum in fact for this test. Please re-read what my issue is.....sorry if I have not been clear.

I am checking the modulator valve per DieselDan writeup. It is the fact that the modulator valve on the transmission is not able to control the transmission hydraulic pressure.

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Dionysius

Cannot help you with the modulator pressure as I've never had to bother with it.

If you decide to leave it alone and chase the vacuum, let me know.

Thanks for your input.

The issue is that the hydraulic pressure which should be settable to 43.5 psi (3 bar ) for this 722.118 transmission is not doable.

I guess I will go and install a new modulator valve to see if this is the problem. Like I said the valve looks like new and reacts when I suck on it. Of course I have no way of verifying its calibration so I am stuck.

To all out there.....Are modulator valves known to go out of cal and react like this??

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Dionysius

The "valve" is a simple piston. I do not see how it can affect the modulator pressure in any way.

Brian,

This is the test I am doing......

Here is the link. It is procedure from DieselDan44 dated June '07. I know you must be familiar with it.

http://www.peachparts.com/Wikka/Trans722VacMod

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Dionysius

Check to see if there is a washer Under the valve on the trans....

Not so long ago a friend had issues with a trans that had been re-built that would not kick down...

There was a copper-washer under that valve causing insufficient movement of the plunger in the trans...

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http://i190.photobucket.com/albums/z...0TDnoplate.jpg

Alastair AKA H.C.II South Wales, U.K. based member

W123, 1985 300TD Wagon, 256K,
-Most recent M.B. purchase, Cost-a-plenty, Gulps BioDiesel extravagantly, and I love it like an old dog.

W114, 1975 280E Custard Yellow,
-Great above decks needs chassis welding--Really will do it this year....

Alastair,

Are you asking if there is a washer causing standoff between modulator valve and trans body?? Answer is no.

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Dionysius

I understand the test, however have not done it personally and cannot provide any feedback of why it won't behave for you.

Dionysius,

Read through your post about testing the modulator valve pressure. My experience is with the 722.315 and later transmissions, but your sounds very similar.

When making the adjustments with the T handle, the gauge movements are very smooth. Based on your description, this was not your experience...

This leads me to think you have a bad modulator valve. Perhaps, as Alastair suggested, it was installed incorrectly.

Either way, if it were me, id buy a new modulator valve (and modulator valve seal), and re-install and re-test. If you get the same results, then maybe your test fixture is faulty, or something is going on in the valve-body of the transmission (I have no experience going in deeper to one of these things)

I ran all over making vacuum adjustments on my fix. But it wasn't until I got my modulator pressure right that the vacuum adjustments worked like they were supposed to.

Good luck, its frustrating...but gratifying if you are able to bring back one of these transmissions back 'from the dead'.

dd

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-------------------------------
'85 300D, 'Lance',250k, ... winter beater (100k on franken-Frybrid 3 Valve Kit)
'82 300D, 'Tex', 228k body / 170k engine ... summer car
'83 300TD Cali Wagon 210k, wife's car

This is an awesome thread! I just picked up a vacuum tester yesterday and will begin working through the solutions here this afternoon. I have an 83 240d with all shifts done by 20mph and no kickdown. I'll bet the answer is in this thread.

Thanks to all who have contributed to make this a great forum

BTW, I tried approaching my local MB stealership for info about the car(which I imported from the USA) and as soon as they eyballed the VIN, I was politely but very firmly told "contact MB USA" as they had no info whatsoever. Is that just a miserable local dealer or a MB Canada policy of being awkward about imports? Makes me not wanna give them any business....

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I choose to be happy, even when the Mercedes is being awkward, lol

I thank you all for your inputs. I am going to get a new modulator valve and repeat tests like DieselDan suggests.

And I will be back to report my results......

I wish I had the time and I would transcribe this thread into a structured and indexed document to help the members.

If some others came up with a draft I would be happy to be an editor. I just have not got the time to do it the way it should be done.

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Dionysius

Does anyone know how the plunger or thrust pin assembly, or whatever it is called, is fastened to the modulator valve part#:1232700679 ???

I do NOT want to brute force it since this has to be transferred on to the new valve diaphragm.

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Dionysius

Ok, I have partially fixed my vacuum trans issues on my 87 190DT. I had a vacuum leak so the trans moudulator did not get a signal. There is a white check valve in the drivers cowl. One side has one nipple the goes to vacuum, the other side has 2. One of the lines is a red w/silver plastic line. It does down by the m/c and cannot find where it goes. What ever is connects to is bad. Any ideas? I cannot find a W201 chassis vacuum diagram. I now have 6" vacuum going to the trans but now it is shifting too soft since I do not have a boost signal to the vacuum amplifier. I am trying to figure out if my VASV or switchover valve is bad.

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1987 190DT, clackity clack
90 Mustang track car
95 Lightning

I recently purchased a 1984 300TDT that has tranny problems. It suffers from a rather severe flares on the second and third shifts. It also had problems shifting into drive early in the day. I dropped the pan, changed the filter, while also draining the converter. The pan and fluid appeared to be fine. Replacing the fluid I added a qt of Marvel. The valve body problem seems to be getting noticeably better. The second and third shift flares have not. I'm trying to get a grip on the vacuum issues. BTW the AC and door locks seem to be pretty good overall. Have the feeling this is a manageable problem between potential leaks (I do have a vac gauge), the K1 spring, the modulator valve, not to mention a bunch of other stuff. Where to start

Greetings,

This is a great site - www.w124performance.com

but it has a problem in that near the very end of the URL the back-slash has been replaced with a front-slash.

Example - here is a manual page for the 124

http://www.w124performance.com/service/w124CD1/Program/main_manual.htm

From here you are offered a number of choices. Let's say I select "Adjusting injection timing - 0761"

I click on it and a new page opens with this URL -

http://www.w124performance.com/service/w124CD1/Program/Maintenance\MY81\0761.pdf

and no page appears.

Now, starting at the end of the URL replace every "\" with "/".

http://www.w124performance.com/service/w124CD1/Program/Maintenance/MY81/0761.pdf

Voila. You may now access the content.