Hey Craig, that was very helpful.  The only part of this procedure I am
slightly wary of is disconnecting and then re-connecting the servo rod to
the locking mechanism:

"...Take the screws off and fish the element out through the hole, twisting
it in a vertical direction to *disconnect its arm from the arm that connects
*to the locks "little flap".
Somese there is a crucial little clip that holds everything together and
likes to fall down into an impenetrable crevice.  I hope that is NOT the
case with the trunk lock mechanism!

Thanks,

Andrew
1985 300CD and 300TD;
1983 300TD

On Tue, Feb 22, 2011 at 11:59 PM, Craig <[email protected]> wrote:

> On Tue, 22 Feb 2011 15:01:56 -0500 andrew strasfogel
> <[email protected]> wrote:
>
> > The vacuum locking system on the 1985 300CD leaks down in about 4 hours
> > after locking the car.
>
> Having trouble-shot the vacuum system on our '82 240D/3.0 over the
> weekend, I have a fresh memory about the system -- I expect the coupe's
> system to be similar to the sedan. Our leaks were so bad, the vacuum
> system could barely shut off the engine.
>
> > Opening the master (driver's door) lock does not result in opening any
> > other door.  (exception:  when the vacuum is lost, the gas flap opens
> > automatically).
>
> That's how things are supposed to work -- the FUEL filler flap is
> single-action, locking only. When it looses locking vacuum, the spring
> included on the vacuum element pushes it to the open position. That way,
> you will always be able to fill the tank.
>
>
> > I have not pinpointed the source of the leak but suspect it's the oldest
> > vacuum element in the car - the trunk lock servo.
>
> That's the one that was leaking on our car -- BOTH the lock and the
> unlock sides! They cost $62.
>
>
> > This morning, I opened the master lock and went back to the (still
> > locked) trunk to open it manually by inserting the key in the lock,
> > turning it clockwise and pushing in the button simultaneously.  The
> > trunk sprung open as expected, but what I did NOT expect was that it
> > REMAINED unlocked afterwards even though the vacuum power had already
> > dissipated.  Can someone explain this?
>
> Ummm ... counterclockwise?
>
> The lock and the vacuum element both move a little flap into position or
> out of position to transfer the inward motion of the button to the
> unlocking mechanism. By opening the trunk with the key, you moved the
> little flap into position and when you pushed on the button, it opened
> the trunk. When you took out the key it was left in position because
> using the key apparently moved the vacuum element's diaphragm, too.
>
> To get to the trunk vacuum element, open the trunk and pry out the
> plastic cover on the vertical portion of the inside of the trunk just to
> the left of the lock. You will be able to see the locking (yellow/red)
> and unlocking (yellow/green) Tecalan hard lines, two pieces of black
> rubber tubing to connect the hard lines to the vacuum element, and the
> vacuum element itself (ours is blue, like in
> http://img.wpac.com/live/thumb/W01331624741VDO.JPG).
>
> The vacuum element is held to the sheet metal by two self-threading
> screws with 8 mm heads. Take the screws off and fish the element out
> through the hole, twisting it in a vertical direction to disconnect its
> arm from the arm that connects to the locks "little flap".
>
> Once you have it out and the hard lines disconnected (DO NOT bend them
> too sharply, they will break), you can check it out with your MityVac.
>
> Right now, pending receipt of the element from Rusty, the two pieces of
> rubber hose for our car are pushed onto the legs of a galvanized fencing
> staple to maintain vacuum-tightness for both the locking and unlocking
> sections of our vacuum system.
>
>
> Craig
>
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