I went to get in my 1984 w123 300D to grab a CD, and as I unlocked the doors, the drivers door was the only door to unlock; the other doors remained locked. I locked the drivers door, and tried again; but again the only door to unlock was the drivers door. So I thought maybe if I ran the car it might fill up the vacuum system reserve so that all of the doors would unlock and lock at the same time (thinking that maybe there wasnt enough pressure in the vacuum system reserve to unlock all of the doors). So I had started the car, ran it at idle for about 30 seconds, and turned the key back to the off position; but the engine kept on running, even after I removed the key from the ignition; so I guess theres a leak in my vacuum system? am I right? What is going on here? And if its the vacuum system, which I am thinking it probably is, how much money do you think it will cost to have repaired? I love this car!!!! It is my first car, it is an 84 model year 300D in immaculate shape in and out (except the vacuum system now :-( It currently has only 106K miles, and I love it so much, I could never imagine being ithout it!!!!!!!! (I did have some oil leaks repaired, and im worried that oil my have/is leaking into the vacuum lines too)
Thanks for the help!

Yes, you definitely have a bad leak in the vacuum system. Since it happened all of a sudden and everything is not working, start by looking for a connector knocked loose somewhere.

There is a good chance that if you inspect all the vacuum lines around the left side of the engine, you will find something knocked off. The most common thing is for one of these connectors to get knocked loose when changing the oil filter. If a thorough inspection does not reveal a loose or damaged vacuum connection, disconnect the brake booster vacuum line and see if the pump is drawing vacuum by simply placing your thumb over the line.

If none of this shows up a leak, post more information here and we will get you through this.

Good luck,

Not too long ago I had some vacuum trouble... and once you get through it... its not all that bad.

I agree with Larry about checking your connectors... the next thing I would do is disconnect the solid yellow vacuum line and plug the other end... see if the engine cuts off right away. This eliminates the engine compartment as being the culprit.

After you are sure it is not a engine leak... it is simply a matter of finding the broken connection (most likely one of the doors). There are vacuum diagrams available in the service manual and if you do a search on this site for this topic you may find some free sources too. But I would then begin to isolate areas but stopping the vacuum from sucking at that door or doors... a good place I found to do this was underneath the carpet on the passagener side. From there I could cut off the trunk, 2 doors, the gas tank all in one swoop. If that allows the engine to cut off... start activating one component at a time. Once you know which one it is... take off the door panel and inspect it for leaks.

I hope this helps a little...

-SB

PS: Good news is that the problem is typically not very expensive parts wise... just take some time.

I would do what the above two suggest, and I had the same experience and it was a catastrophic sudden vacuum loss, and not gradual.

In my case one of the plastic vacuum lines that feeds through to the drivers door lock from the dash snapped in half.

The rubber tube that you can see when you open the drivers door, between the pillar and the door by the hinges gets a lot of action from opening and closing the drivers door. It has the vacuum tubes in it and one of mine was broken. I put a small rubber vacuum hose over the two sections for a repair.