I have a 1984 300CD and the vacuum hose connections for the car body systems were all in a rats nest of fittings in bad shape. I would like some help putting it all back in place please. At the firewall there are 5 lines for the systems as I see it. They are:

1. Door lock system
2. Seat Back lock system (coupe only)
3. HVAC system
4. Fuel shutoff system

The 5th line is the Vacuum Reservoir tank line.

My main question: Do all 4 systems connect to both the vacuum pump line and to the reservoir line through the use of the 2/3 way yellow check valves, one valve per system?

2nd question: The vacuum pump suction line that runs to the brake booster has 2 tee connections. Is it correct that the intake manifold pressure system connects to the tee connection closer to the vacuum pump and the car systems above connect to the tee connection closest to the brake booster that is actually on the check valve in the main line?

If I can get this straight I believe I will be in much better shape. I had so many leaks that the engine would not shut off via the key switch. The worst leak was the drivers side door lock/unlock valve.

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1984 300CD (sold)
1973 220DPK 4 spd (died)
1978 350SL 4 spd gray market
2003 SLK32 AMG
1988 300CE (sold)
1997 E420 (Totaled)
1998 E320 Wagon

There is no vacuum connection to the Intake Manifold as your Diesel Engine has no Vacuum in the intake Manifold.

The line that starts at the very back of the Intake Manifold goes to a small overload valve on the Fire Wall and a line from there goes to the ALDA on top of the fuel Injection Pump.

One of the lines going through the Fire Wall on my 300D is Black and it connects to nothing because it is a vent line andis therefore open.

I believe the seat line is Blue.

Vacuum Diagrams look here if the site still works: W123 Service Manual
https://www.startekinfo.com/StarTek/outside/12265/?requestedDocId=12265

In the diagram below I believe the color represents the color of the strip that is on the vacuum line.

Except for the 3 and 4 way connectors the rest of the connectors are just short pieces of vacuum line that you could cut off a length off of yourself.

If you want something bettern then the typical vacuum hose you could use Silicon Vacuum Hose.
The Plastic Vacuum tubing can be replace by any nylon or plastic tubing that is aproximatly the same size as long as the connectors can seal on them.
But, replacing the plastic tubing means the loss of the color coding.

Attached Thumbnails

 

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84 300D, 82 Volvo 244Gl Diesel

Search on this site for vacuum hose diagrams. There are several good ones though none speifically for a coupe. As you stated the coupe has the additional vacuum tube for the seat locks.

Here is a Google search I did.

https://www.google.com/search?q=mercedes+84+300CD+vacuum+diagram&biw=881&bih=420&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjehP2K8JHPAhUU84MKHRZxBHAQ_AUIBigB#imgrc=Vp7p81h6EAv2HM%3A

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there were three HP ratings on the OM616...

1) Not much power
2) Even less power
3) Not nearly enough power!! 240D w/auto

Anyone that thinks a 240D is slow drives too fast.

80 240D Naturally Exasperated, 4-Spd 388k DD 150mph spedo 3:58 Diff

We are advised to NOT judge ALL Muslims by the actions of a few lunatics, but we are encouraged to judge ALL gun owners by the actions of a few lunatics. Funny how that works