1980 Mercedes 300CD Vacuum leak?

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tomjm - 06 Dec 2005 05:30 GMT

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?

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The Spanish Inquisition - 06 Dec 2005 06:08 GMT

> New to mercedes, not used to all the vacuum lines
>
[quoted text clipped - 10 lines]
>
> How do I proceed?

Have a look at this, maybe:

http://engine.articles.mbz.org/both/vacuum/

Ximinez

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T.G. Lambach - 06 Dec 2005 07:35 GMT

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
www.performanceproducts.com. 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: http://www.tmcpubl.com//mercedes.html or
http://www.books4cars.com/

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Darrell with DieselBenz.info - 08 Dec 2005 03:52 GMT

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

http://www.dieselbenz.info/dieseling_index.htm

>New to mercedes, not used to all the vacuum lines
>
[quoted text clipped - 12 lines]
>
>

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thanks,
Darrell

http://www.dieselbenz.info/

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