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Marty
Marty, Mercedes Technician
Category: Mercedes
Satisfied Customers: 53676
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 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 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.