[phantoms]

Here are some vacuum diagrams to help you diagnose your W123, W124 or W126 diesels. The 240D diagrams were looked up for a 83 year model, but should be pretty much the same for 82-85. I've also added some wiring and flow diagrams. Also note that there are year to year (and sometimes, throughout the year) changes and these diagrams may not reflect everything exactly as on your model.

'86-'87 300 SDL, '87 300D vacuum diagram


85 300D and 85 300SD California emissions Fuel & EGR vacuum diagram
84 300D and 300SD California emissions Fuel & EGR vacuum diagram
81-84 300D and 300SD Fuel & EGR vacuum diagram.

82 & up 240D Fuel and EGR (Automatic trans) vacuum diagram
82 & up 240D Fuel and EGR (Manual trans) vacuum diagram

IP Shutoff system diagram
Fuel Mixture Control diagram
Fuel Filter and Connections diagram
Injector Parts diagram
Turbo system diagram

Heating and AC diagram
240D AC diagram

Steering/Ignition Lock Assembly diagram

Automatic Transmission Shift Selector Gear Functions
722.3 Automatic Transmission Gear Ratios
722.3 Automatic Transmission Vacuum Function and Control

Central Interlock System diagram for Chassis 123.1, 123.02/03
Central Interlock Circuit diagram for Chassis 123.1
Central Interlock Circuit diagram for Chassis 123.02/03

Central Interlock System diagram for Chassis 123.183/190
Central Interlock Circuit diagram for Chassis 123.183/190

Cruise Control and Stop Lights wiring diagram
Power window and switches wiring diagram (part1)
Power window and switches wiring diagram (part2)

Coolant Flow diagram
Engine Lubrication diagram

Installing a Fast Start Glowplug kit (changing from loop to pencil style glowplugs)

Edit:http://www.peterschmidtransmission.com/vacuum.htm also has a good deal of vacuum diagrams available.