I bought an 82 240D last fall...one owner, well looked after. Recently the engine remained running even though ignition had been shut off. My mechanic determined the vacuum pump needed replacing and did so. Engine shut off for about 3 days but then it kept running on after key turned off. He's blocked the vacuum lines going to the door locks and trunk. Now the engine shuts off but I miss the door lock feature. Have the lines gotten old and collapsed? Is it a big deal to locate and replace? Is it something I could do myself?
Thanks.

Welcome to the funky vacuum "Central Locking System" in MB terminology.

The dreaded vacuum leaks that occur in many older MB's can scare some people away from having repairs done, especially if the shops quote a real high price for labor based on not knowing exactly what needs to be done.

This is a DIY job if you have a little time and a vac gauge like the Mity Vac. The best Mity Vac will run about $60 and lesser models (plastic body instead of metal) are around $35, and allow you to apply vacuum with the hand pump and watch the vac level to see that it holds or not. It is a very necessary tool unless you want to $hotgun a lot of part$
Also! Please use the search feature, enter MityVac or similar and read more about this subject.

The parts that usually fail are vacuum diaphragms in the door lock actuators, and are not difficult to change. Getting the front door panels off without breaking the door pockets is tricky. you basically need to not pop off the lower front tabs (the rest of the door panels use pop-off clips. A wide screwdriver will serve as a tool or my favorite tool is a putty knife.

New parts cost is about $57 per door for the OE style vac elements. There are (were?) kits that consist of replacement rubber diaphragms. I still have some but they are not fun to install. IMO.

I knew someone who repaired diaphragms, if they were slightly cracked (not torn) he dabbed some 3M rubber compound on them, the stuff comes in a can and is sold for high voltage insulation at places like Granger, but that is a long shot. I have been lucky in finding elements at a wrecking yard, take them out of the doors when you find a crashed door, they almost give them away!
I either use a complete element that is in good condition or buy a new OE replacement, depending on the car (my own cars I used take offs OK with no problem but I know I am on borrowed time with that approach).

Oh yes, there is a vac element for the fuel filler door and one for the trunk lock, both of these should be checked and are quite easy and should be checked before tearing into the doors.
Good Luck!

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'95 E320 Wagon my favorite road car. '99 E300D wolf in sheeps body, '87 300D Sportline suspension, '79 300TD w/ 617.952 engine at 367,750 and counting!

I recently had the same problems with my 83 I bought 3 months ago and have slowly replaced all the vacuum lines and rubber connectors in the entire car (not plastic). It is a fairly inexpensive routine and at one point the car wouldn't turn off unless I opened the drivers door (?) and kept replacing them and eventually all the problems went away. When I was all done I bought a new mityvac and tomorrow I am going to check what amount of vacuum is being produced by my pump as I think it is low (tranny is weird). Everytime I replaced major rubber lines the car just kept running better and better and now it is just about perfect....I would recommend replacing all of the rubber lines and connectors and then you would be done with it....

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83 300CDTurbo 307,000
2005 Honda Element 266,000
56 Nash Ambassador Country Club Special 34,000(under restoration presently)

http://www.peachparts.com/shopforum/car-audio-multimedia/125099-123-install-extreme-dynamat.html

Unfortunately, there are a lot of other rubber components in the door lock and climate control actuators that tend to leak. Those items contain diaphragms that flex with operation and are much more subject to "wear and tear" than hoses and connectors.

Just an update on testing with the MityVac and indeed Tangofox007 is right as I found both the diaphrams for the door locks leaking (one really bad) and the trunk lock also...When I plug them in the engine compartment the tranny shifts better and I have a harder brake pedal. Ah the wonders of vacuum....

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83 300CDTurbo 307,000
2005 Honda Element 266,000
56 Nash Ambassador Country Club Special 34,000(under restoration presently)

http://www.peachparts.com/shopforum/showthread.php?t=125099

Yo dieseldorf.....Me thinks we've met via freds and an exchange of a plastic underbelly pan for a VW TDI.....If not I must have been sucking too many diesel fumes....Anyhow. I suggest you and I get togtehr and takle some similar vac. issues together. I've got a mityvac and as soon as I get my buggered engine hanger fixed I'll be able to rol the car out of the garage for cleaning and then vac. troubleshooting.....

Rob M golf TDI
&

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Rob M
Norwich, VT USA
1980 240D Euro delivery 4 speed manual silver/blue
~160K miles