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1980 Mercedes 300CD Vacuum leak?

New to mercedes, not used to all the vacuum lines

  1. Engine does not want to turn off. Usually will turn off if you gun the engine right before turning the key.However, I just replaced the brake pads and now I find after a quick test drive that I have a hard pedal and that the car will not turn off at all.
  2. Various devices that run on vacuum do not work properly, especially if car has been sitting - automatic door locks etc.
  3. Fan is constantly blowing low into car. Will blow harder if you turn AC/heater to hi, but will not shut off completely when you turn to "off". Dont know whether this has to do with vacuum or not; everything else in this car seems to, so ...

How do I proceed?

Reply to
tomjm
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Have a look at this, maybe:

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Ximinez

Reply to
The Spanish Inquisition

Get a vacuum schematic and a vacuum pump/tester; many owners use a Mity Vac (may not be spelled correctly).

There's a vacuum pump on the front of the engine. You can rebuild the pump with a kit.

Vacuum is used for:

Power Brakes Transmission's shift modulation Climate control Engine shut down Door locks.

Your car has a significant vacuum leak or a bad vacuum pump. Start with the pump (source) and check if it's making vacuum, then work your way through the system.

Climate control has a "cold engine lockout" a bimetallic vacuum switch on the very, very bottom of the climate control servo that's supposed to keep the heater OFF until the heater core is warm enough to provide heat. The bimetallic switch can be jumped. Blower's ON/OFF is also controlled by a vacuum switch.

Climate control system has two major parts: its logic board "amplifier" and its valve body, including vacuum, "servo". If you find or are told that the climate control "servo" is bad I suggest you consider a digital retrofit kit that's sold by

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I put one on my '80 300SD.

They also have a repair parts catalog for your model that includes exploded parts diagrams and may also include a vacuum schematic.

You may find manuals at:

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or
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Reply to
T.G. Lambach

It is this VERY question I made my site for!!!

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tomjm wrote:

Reply to
Darrell with DieselBenz.info

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