Hello everyone. I just bought my first M-B yesterday, so I'm brand new. I have a beautiful 1984 300cd with 170k. Although I love the car, it does have pretty hard 1-2 shifts and it doesn't seem to have any power. I have done some reading and today I did some investigation. I would really appreciate some input here from the more experienced members. I'm primarily trying to improve the really harsh shifting. Here's what I did/ found:

1. I checked the vacuum lines with a mityvac. Everything seems to hold vacuum well except for one line that slowly drains vaccum. Strangely, (or maybe not) the vacuum drain makes a weird moaning noise from some small component on the front passenger fender - not sure what this is yet. Also, someone had plugged one of the black lines coming off of this component - I reconnected it.

2. I cleaned the banjo bolt. The line from the banjo bolt to the switchover unit had been removed and plugged up with a screw for some reason. The banjo bolt was completely occluded with gunk, so I cleaned it up and will reattach it tomorrow. Unfortunately, the pressure line was brittle and snapped in two, so I will have to find some kind of replacement line tomorrow. Any suggestions?

3. Also, when I am in the car, the door locks cannot be moved by hand on either door- is this normal? The key works to lock both doors from the outside, but the door locks on the inside feel like they are stuck. Does this have anything to do with the vacuum system too or is this an unrelated issue?

Any other suggestions on how to improve the shifting? I was thinking that maybe the car is not getting enough power due to the ALDA system not being functional. My hope is that when I get the lines hooked back up tomorrow, more power will be the result and the shifting may improve. Anything else I can try?

update:

I found some hose that is the same diameter as the previous tubing that connected the banjo bolt to the switchover unit. Unfortunately, I couldn't find any tubing as hard as the plastic tubing that was on before so I am using some more flexible black rubbery tubing. It is still fairly firm so I don't think/ hope this will be an issue. The door locks seem to work now so I am hoping that issue is resolved. I took the car for a short spin this morning and I can't tell if there is anymore power (doesn't seem like it), and the shifting is still pretty jarring. Next I'm going to do a valve adjustment. Any other suggestions happily accepted.

Don't draw a vacuum on the ALDA!

Sixto
MB-less

The door lock tabs on the CDs are a unique design to the Coupe and seem to get sticky. I seem to recall on my Coupe this caused the inside handle to bind a bit as well.

Remove the door panel and lube the entire lock and door handle assembly and linkages.

It is not a vacuum issue.

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Mac
2002 e320 4matic estate│1985 300d│1980 300td
Previous: 1979 & 1982 & 1983 300sd │ 1982 240d

“Let's take a drive into the middle of nowhere with a packet of Marlboro lights and talk about our lives.” ― Joseph Heller, Catch-22

You do not use vacuum to upshift; it is only for a smooth downshift. In fact the vacuum is supposed to go to zero quickly when you hit the accelerator, called WOT or wide open throttle.

Is there a vacuum proportioning valve on a 123? I thought that was only in 60x and later motors.

This is the function of the VCV, the white valve bolted to the top of the injection pump and connected to the throttle linkage.

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Mac
2002 e320 4matic estate│1985 300d│1980 300td
Previous: 1979 & 1982 & 1983 300sd │ 1982 240d

“Let's take a drive into the middle of nowhere with a packet of Marlboro lights and talk about our lives.” ― Joseph Heller, Catch-22

I didn't realize this. So if I understand correctly, any potential vacuum problems I may or may not have are unrelated to the hard upshifts. To me this means that either the engine needs to be tuned in some way, the transmission needs to be adjusted in some way, or a little of both perhaps. I think I will discontinue my interest in the vacuum system for now.

Today I started my next project - valve adjustment. I got halfway through before I quit and went online to order some valve adjustment wrenches. If it can be done with straight open ended wrenches, I can't imagine how. My hope is that this will help with the power and shifting problems. I was disappointed with the lack of results from cleaning and reattaching the banjo bolt and associated pressure line.

Thanks, it doesn't seem to be consistently stuck only sometimes. Your advice seems reasonable - thanks I'll give it a try.

I did not know I knocked off the Vacuum Line to the Transmiddion Modulator and the up shifts were almost the same but the down shifts were jarring.

Transmission Vacuum and adjustments
Mercedes-Benz Transmission, Steve Brotherton, ImportCar, February 2002

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84 300D, 82 Volvo 244Gl Diesel