Question about 1985 Mercedes-Benz 300

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1985 Mercedes 300D vacuum problem

The vacuum system seems to be messed up; the engine sometimes takes almost a minute to shut off; I had someome disconnect something so it would turn off immediately after turing the ignition off & it make my door locks not work (could not even manually lock the car); also the air will not blow thru the 2 center vents; I was told this was a vacuum problem.

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  • Anonymous Mar 24, 2014

    door lock vacuum pump dose not work



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Hello, Your vacuum was probably shut off at the yellow valves located near the accelerator shaft at the firewall. Lines from these valves supply vacuum to the door lock system and storage tank. If the engine would not shut off with these connected. one or more of the door lock servo's are leaking. You have a servo in each door, one on the gas lid and one controls the trunk lock. You can pull up the front floor mats and use a hand held vacuum tester to start checking to see which servo is leaking.
As far as your vent problem, you problem have a bad climate control servo or switchover valve.
If you find this information to be correct would you please enter a "fixya" rating.
Thanks, Gator241

Posted on Feb 14, 2009


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Vacuum diagram of Mercedes 190D, 2,2

neto 190D: You are asking about a vacuum diaphragm?
I'm going to take a WAG.. Your engine won't shut
down with the key?
If so, he is the way you find out:
In your injection pump, the vacuum diaphragm which kills the engine is the one which has the fitting pointing parallel to the ground.
The vacuum line which serves it is a brown/blue
To check the system, first check for vacuum in the line. Run the engine for a minute or so. Cap off the brown/blue line.
Turn the ignition switch off and then with hose in hand, uncap it and you should hear a hissing sound. If you have a vacuum guage, obviously, use it for the test, you need a minimum of 10 inches to kill it.
To test the pump diaphragm, you can rig a vacuum line to a known vacuum source close to the main "T". Run the engine and with the line connected to the diaphragm, connect it to the good vacuum source, if it kill the engine, the diaphragm is good. If you have a hand vacuum pump it would be more ideal, because you could check the diaphragm for small leaks.
If the diaphragm is bad, it is easy to replace on the pump.
The shutoff diaphragm lists for $86.00
Is my shot in the dark correct?
Even though I am a Nissan Master tech, I also specialize in Mercedes-Benz and specifically Diesels, so if you need help, I'm here. I went through a few Mercedes Schools and have been swinging Iron in Mercedes since the 70's
I might be a little more informative than the public library.

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