I just recently aquired a 1980 300cd with 128,000 miles. It has been very well maintained as it was owned by a consulate of Peru. I was working under the dash removing an old alarm system when I knocked some vacuum lines loose. The engine now does not shut off by key and I have to manually shut it off. I have two brown vacuum lines going into the ingition switch and I saw that one goes into the switch for the fuel, uncertain about name of part but it is white and plastic, and a black line that runs from the side of the white plastic part into the cab. However, I do not know where that black(I guess shut off line)goes. I removed the center console and there was two lines that did have a connector attached to them. the first one is black and is short and is coming out from the bottom end of the AC control unit, the second is a green striped line that is attached to a connector comming off of the master cylinder line that ends underneath the AC unit control inside the cab. These two lines did not look like they were connected at one time nor does the black line connected to the white plastic part(fuel valve?) long enough to go to the AC control unit. It is long enough to connect to the inginition switch. Have I connected the lines wrong or am I missing a y-connector? Need some help please.

I know your pain

Where is it leaking from.
My thoughts
1 The vacuum line that goes from the vacuum pump to the brake booster should have two inserts for vacuum access.

2 Those lines should be secure and vacuum tight You might have them nocked off

3 The black line that goes into the cabin does not attatch to anything it is for leakage of the vacuum system

4 Your shut off valve unit should have three vacuum lines going to them. Your brown line from your ignition goes to a nipple located between the shut off valve(fuel pump) and the oil filter... IT is a tight fit and sometimes they come off when you are doing an oil change.

That should get you started.

good luck

bob

Thanks Bob, you were a great help. I was able to fix, temporarily, I have oil in the system so I guess the (engine vacuum shut off valve?) is bad and needs replacing. It seems that every time I take something apart, I notice something else that needs to be fixed. Oh the joy. I was able to remove the valve and clean as a temporary fix. At least I now know how most of the vacuum system works(trial and error).

However, I have two follow-on questions. My first one is the green line that goes into the cabin from the main vacuum line from the brake booster. Where exactly does it plug into. It is now capped off as to keep vacuum up. I have read that it is connected to the climate control system. There are five lines to the climate control system. From top to bottom they are blue(top), purple, black, and blue(bottom, capped off?). One black line by itself, same unit next to the four other lines. Does the green line connect to one of these? The purple is accounted for, but the others are connected to? When I bought the car the controls worked fine, however that the AC was not cold. The secondary fan came on as the AC was turned on and all the other settings worked. Now just the defrost. works and I do not know that I hooked the line up correctly when I was back there working. I need help on this as I do not have a diagram yet.

Secondly, there are two vacuum lines coming from a control unit in the front pass. engine compartment, I guess it is the AC control unit that everyone has been complaining about in these vehicles. They are black and white and are broken off, they led into the cab but were cut. It did not look as if they were going anywhere as they were short in length. Need help here as well. I have capped them just in case.

Thanks for all your help, especially the archives, great info.

The green line goes to the climate control unit, actually it goes to a five branched dispersment unit that connects to the switchover valves that the control unit controls. You might have a leak in one of the vacuum elements of the climate control unit.

Anyway you have other fish to fry before you go after that. You have oil in the system. I dont know about that maybe it is a faulty vacuum pump. Do a search on that. That would be my first order of repair.

Heres what I do know
green is climate control
yellow is door locks
yellow with black strip is vacuum resevior
brown is fuel shut off

The other vacuum lines I am not as sure about. I have yet to brake them but I will get around to It.

They are for the enviromental controls ERG valve ect.

CLose off the systems that are not crutial and isolate your problems.

IF you like you can Email me your fax number and i can send you some diagrams of what this stuff should look like.

It looks like your car has been butchered a little.

Good luck

bob