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Marty
Marty, Mercedes Technician
Category: Mercedes
Satisfied Customers: 53303
Experience:  Bosch Certified Master Tech. Over 35 years experience.
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Mercedes-Benz 450SL 1975 Mercedes 450 SL looking for a vacuum

Resolved Question:

1975 Mercedes 450 SL looking for a vacuum routing diagram for the 3 electric vacuum solenoids and the one vacuum distributor that are in a cluster on the passenger front fender.

Can anyone help?
Submitted: 5 years ago.
Category: Mercedes
Expert:  Marty replied 5 years ago.
Hi, click on the image below for the vacuum diagram of the system.

graphic
Customer: replied 5 years ago.
That is fantastic. I have been searching for hours and I have two manuals which are mum on the subject. The only question I have is with the "vacuum control switch" - mine has 4 lines as opposed to the three in the diagram. I did forget to mention that this is a California vehicle. Not sure if that makes a difference.

Tom
Expert:  Marty replied 5 years ago.
Hi Tom, I only show the three lines. I'd work through the diagram and see where the 4th line falls. Let me know if you run into trouble.
Marty and 2 other Mercedes Specialists are ready to help you
Customer: replied 5 years ago.
Will do - thank you so much.

Tom
Expert:  Marty replied 5 years ago.
Hi Tom, I found some more info. It provides a little more detail for you. Click on the link.

Emission Control System

Customer: replied 5 years ago.
Thank you again. I appreciate it.

Tom
Expert:  Marty replied 5 years ago.
You're welcome
Customer: replied 5 years ago.
Hi,

Thanks to your great diagrams, I have the vacuum lines all sorted out. Here is my problem now. I get no vacuum advance to the distributor from the red solenoid, # XXXXX on your last diagram. I do get vacuum if I disconnect the power plug from the solenoid, so it must be a normally open unless energized. Since all the power plugs run parallel, all the solenoids must get energized at the same time.

I did test the retard solenoid, but since the engine was already warmed up, I am not sure if I should have seen vacuum or not - I did not.

All the source vacuum is connected to the center ports of the solenoids.

Thank you
Tom
Expert:  Marty replied 5 years ago.
Hi Tom, go to page 6 in the second set of instructions I gave you and check the temperature switch at the back of the intake manifold. It opens over 40°C and turns off the solenoid to give you EGR and vacuum advance.
Marty and 2 other Mercedes Specialists are ready to help you
Customer: replied 5 years ago.
Got it. I guess the 3 vacuum solenoids are not all activated at the same time, just looks like it from the parallel connectors.