The vacuum system completely blew yesterday! I could hear it hissing from under the dash or in the drivers door. Locks don't work and engine needs to be manually shut off.

How soon and how much will this affect the braking system?
I am going out after this post to to start tearing into it (removing interior panels etc). The leak is so bad that even with the engine revved I get nothing!

I used the 'search' and did not find any thing that mentioned this scenario. Lots of help with diagnosis and fixes. Where do you get the mentioned 'diaphrams'. They are not on 'fastlane'

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1982 240D 313,000 (4 speed)
1984 300CD 172,483
1985 German Shepherd Dog -Lacey- R.I.P.11/04/05

Hood Stars, Wrist Crowns and Obsession Dobs

the bern,

If you have brakes now, the chances are your car's vacuum pump diaphragm is ok. In addition, there are little check valves in the lines going to the services that have failed that isolate the brakes from some of the leaks you have. These check valves can get old and fail too, so I don't want you to think things are ok forever. But I would not expect a brake failure to be your next experience as in general the vacuum pump capacity is enough to make up for the leaks in the smaller lines to all the vacuum system services. A failure close to the connection to the brake booster poses more danger than the connector out at a door or the trunk lock, for example. (edit)

I am a hack at fixing the vacuum system and have disconnected the locks on the 1982 240D rather than fix them. So I am not a valid source of trouble shooting information here. I have had the fuel injection pump shutoff diaphragm let go, and allow oil to get into the vacuum switch on the back of the starter key mechanism, which eventually resulted in the swelling of the rubber connector to the point where the vacuum line fell off. I do not recall audible hissing though, so I had to kind of poke around a lot. You, on the other hand, can probably track the leak down easier by finding where the hissing is coming from, and then isolate the leak and see if the engine shuts off again, and the locks work (isolating the leak may also disconnect the locks from the locking system, so they may not work - but you will know what the bum part it is and what to do to replace it).

Luckily vacuum stuff is relatively inexpensive so the biggest problem is getting to the broken part. This is a potential source of much frustration as the vacuum system goes everywhere.

Good luck, Jim

__________________
Own:
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles

Owned:
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)

The first thing that I would do is to plug one of the lines that come off the yellow plastic one to two way check valve on the engine side of the firewall. One of the two lines that come off that valve (yellow with a red stripe ?- check the vac diagram) will supply vacuum to the locks. Plug it and (hopefully) your car will shut off and otherwise work and let you sleep until you can take your time and troubleshoot the central locking system.

If you don't already have it, the cd from MB has a lot of good info on troubleshooting the vac sys.

best of luck

__________________
84 300TD - 235k - Farbe "Surfblau" bought at 213k
87 300SDL - 131k - Farbe "PimpGold" bought at 115k
00 Klepper Faltboot Expedition Double

The bern,

These's a very good booklet on the vacuum system from www.**************.com . They often have it advertised on ebay, where they have literally pages of stuff for Mercedes.

The brown lines running through the firewall are to and from the ignition switch and the shutoff switch on the injector pump. The two yellow lines are the lines to and from the lock system. The yellow with green stripe is the unlock flow and the yellow with red is the lock. (Remember stop and go light system.) Logical these Germans. Green goes to the heater/a/c controls.

If you block off everything but the brown and brakes and everything works, then it's almost certain to be one of the locks. You can block them off under the carpets on the passenger side.

Did you have your oil changed recently? Often the oil changers knock off the vacuum connections and then either don't plug them in or plug them in wrong.

Hope this helps. Get the manual
Ben