From what i have seen on this board my 1983 300 d has a leak. the door locks do not work & the transmission shifts really hard. my question is WHERE SHOULD I START LOOKING? i bought a mighty vac but will have to rely on you guys to get started.
thanks, paul

My experience in trying to track down a leak may help you at least to get started. My locks were sluggish and I found that sometimes the engine wouldn't shut off properly. First I very closely checked all rubber connectors in the engine compartment, especially near the driver's side firewall. Sometimes these crack or become disconnected when you pull out the oil filter. Second I tested all the functions of the ventilation system. As I did this I discovered that my center dash vents were not working. I pulled the front panel off the climate control and carefully pulled out the push button panel so I could access the vacuum lines. I then used my Mighty Vac and tested them one at a time (be really careful not to mix them up) to see if one or more of the vacuum actuaters/servos wouldn't hold a vacuum. Needless to say I discovered one of my vacuum servos was leaking. Just to be sure that was really the problem I checked by pinching the line to the faulty servo and with the engine running tried the locks and engine shutoff. Voila, everything worked perfectly. That one leak was enough to affect the whole system. It was a time consuming, pain in the you know what job but it worked. You just have to start at one end and move toward the other until you find something. In my case I got lucky and saved time by checking very carefully to see if some vacuum driven item was barely working or not working at all. If you find that, it's an obvious place to focus. If someone else has a shortcut I'd love to hear it but my guess is this is just one of those slow, methodical jobs that eats up time. Good luck!

lrg

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LRG
1987 300D Turbo 175K
2006 Toyota Prius, efficent but no soul
1985 300 TDT(130K miles of trouble free motoring)now sold

I just replaced three of my vacuum servos, all of which were bad and creating a myriad of what seemed to unassociated problems. I also ordered about two dozen 90 degree vacuum lines and other connections from Fastlane and just started replacing them all. Most of them were dry rotted and their ability to hold vacuum under all temperature extremes was suspect.
As far as troubleshooting vacuum problems, experience definitely helps in regard to knowing what to look at first - but definitely not necessary. Look around at all the vacuum connections under the hood, replace whatever you can afford remembering that this vehicle is 17+ years old. Then, look under the dash and check the servos behind the panel that holds four switches (antennae, rear defrost, etc.). I was able to replace my servos simply by removing this panel and glove box all in about 30 minutes. While you have thie panel off, replace all the acc lights, as they are likely to be bad, or on their way out. With thew glove box out, look around at the vacuum operated diaphrams for their operation while depressing different buttons to ensure their operation and listen for a click from their associated servo. If this doesn't work, check the vacuum res. in the trunk. The good thing about vacuum leaks is that they typically make noise, so listen up for anything unusual. hmmm, I guess there are more places to look, but this should help for now. Good luck - ain't it fun?? Adam 1985 300d cali model 140k nearly perfect

Paul:

There are four sets of vacuum lines in your car that run from the main vaccuum line to various other things.

MB uses hard plastic lines with rubber connectors, and the lines are colored

The maim line is large and runs from the vaccuum pump at the front of the engine to the brake booster, about 5/8" diameter. combination of steel and plastic hose.

On the mail line there are three fittings:

Green hard plastic line with check valve at firewall -- this is for the climate controls

Yellow hard plastic with check valve at firewall -- this is for the lock system. There is a control valve in the driver's door, from which there is a yellow with red stripe line and a yellow with green stripe line to each actuator -- one in each door, one for the trunk lid, and one for the filler cap.

Brown with blue stripe -- this goes to the ignition switch and is for the cutoff. Brown line goes to the cutoff (or they are reversed, I can never keep these two straight).

White hard plastic line (with little yellow or blue plastic insert (restriction) that goes to a box on the valve cover and to the transmission -- this is the vacuum modulator control line.

Check all the rubber ends -- I expect that they will be all either rock hard and loose or very soft and shedding black powder, and leaking. Check that the restriction for the transmission isn't plugged -- it's just a small hole in the plastic bit.

You can replace all the ends with standard vaccuum line from the auto parts store, or buy replacements from FastLane or other supplier. I would buy the three-way "t"s and other oddball connectors from an OEM supplier. Don't forget to check for filters or restrictions -- they will be small plastic "inserts" that look like plain connectors -- keep them and put them back where they were.

You may also find some broken hard plastic lines -- they can be spliced with standard vacuum line.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

Thanks to all for the info. I think I better wait until I have a full day to start this search.As you can tell I'm a novice at this so I knowI will be back for more help. I love my 300d but could not afford to keep it with out the help I've gotten from this board.
Thanks, Paul