Mighty-vac time on the vacuum line that branches off from the "pod' before the master cylinder with the engine running and the key in the off posistion.

But, I have not found any leaks or disconnected vacuum hoses yet. Still looking and may go back to the same shop next week. I will try to hold them at least partially responsible since I was not asked whether I wanted a power wash. I have never done that -and for this very reason. I still wonder whether the earlier glow plug change is related to the leaking fuel line from the injector to the back cylinder.

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87 300D 265Kmi
Factory rebuilt crate 603.96x engine at 200K

The locking system is isolated, so if the check valve is working properly you can actually unplug the line to the locks and they'll still function until you use up the vacuum.

It's gotta be a leak or loose line.

-Rog

Your car is a 124 chassis the engine vacuum system has nothing to do with door/trunk/fuel door locking or unlocking. Those are all actuated and controlled by the electrically operated vacuum pump located under the rear seat on the passenger side inside a foam protector.

Engine shut-off and shifting (as well as brake booster and climate control) uses vacuum produced by the engine powered mechanical vacuum pump located at the front of the engine.

Found a brown vacuum line disconnected-apparently the one returning from the ignition switch (duh). Reconnected and, after several failed shut down attempts and some driving, it now shuts off. It takes a few seconds but does eventually shut down normally. This did not resolve the harsh shifting which is more harsh on downshifts particularly the last one before stopping. Since this line must have been disconnected accidentally by the shop that did the glow plug replacement (which involved removing the intake manifold) and the fuel line replacement, I am taking it back there tomorrow. Will post results when available.

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87 300D 265Kmi
Factory rebuilt crate 603.96x engine at 200K

There is a black line that goes from the VCV (a white plastic contraption sitting on top/back side of IP and controlled by the throttle linkage - also should have a green dashpot coming off top) to the vacuum modulator on the transmission. I this line is disconnected or leaking, you will get the harsh downshift on that last one - can sound like something is banging under the car when you come to a stop.

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Andrew
Montclair, NJ
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1982 300D Turbo
120k
Petrol Blue Green

It actually feel like the whole rear axle is trying to come out from under the car in that last shift. Does this black line appear from the engine compartment or is it necessary to put the car on a lift to see where the black line attaches to the transmission?

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87 300D 265Kmi
Factory rebuilt crate 603.96x engine at 200K

Your car is designed to bleed off vac for a smooth upshift. It only needs vac for a downshift. If you are getting clunky downshifts, you just have a vac leak. It is working properly.

The shop found 3 disconnected hoses and several that were plugged. They do not know where the disconnected ones go. One is black so I had them check whether there was a black vacuum line attached to the transmission. I have not heard back on that but their immediate response is that there is a modulator on the transmission that includes a diaphragm. Sometimes, they said that diaphragm starts leaking and sucks up transmission fluid. Should know later today.

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87 300D 265Kmi
Factory rebuilt crate 603.96x engine at 200K

There is one black line that is used as a vent. Normally, it goes inside the cabin. It needs no connection. From what they are saying, I'm guessing they aren't very familiar with the older diesels.

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Sam

84 300SD 350K+ miles ( Blue Belle )

If yours is like my SD, it sounds like the previous owner disconnected the EGR hoses and plugged them. That is fine. You just need vac to the VCV and to the vac modulator to make it shift right. Do not need the EGR works.

On a 300D (not quite sure about SD) - the vac line from the VCV to the transmission modulator is also black. you have to get under the car to access it, as it is in the side of the tranny in the transmission tunnel - don't need it on a lift, but most definitely ramps or jack stands.

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Andrew
Montclair, NJ
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1982 300D Turbo
120k
Petrol Blue Green

Again if you are having clunky downshifts, it may just be a vac leak. If you hook a Mityvac in the line going to the vac modulator, you can drive it around; after it upshifts, pump up vac on the Mityvac and then come to a stop. The tranny should downshift just fine if you have pumped up the vac in the line with the Mityvac - assuming of course that it holds a vac.

I took the car in for an appointment on Wednesday. On Thursday afternoon, I was told that they had not gotten to it yet. This led me to believe that, since the vacuum problem was demonstrably caused by the shop's decision to power wash the engine bay, they knew that this would be a freebie and it went to the back of the line. I got the car back from them to let them know that I was not satisfied with the service that they were providing. I guess that I will have to take it back there with the understanding that, if make an appointment, they will work on the car at that time. I really have no idea how to trace down a vacuum leak and have no MityVac to do it with if I did know what I was doing. Luckily, I have a couple other cars.

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87 300D 265Kmi
Factory rebuilt crate 603.96x engine at 200K

As I remember the Mityvac is about $25. I have found it to be a good investment over the years. You may need it in stage future if you keep the car.