I know this is a long post, but I would appriciate any help.

I am getting tired of chasing vacuum leaks and I am sure you all are experienced in this feeling. I am still having problems. Here's the story. My 82 300TD has the typical vacuum symptoms, doesn't shut down quickly (most of the time), the door locks don't all work. Brakes seem to work okay, they are a little hard, but not bad. Shifting is hard sometimes, usually when accelerating slowly, when I speed up quickly the shifting is smoother.

Here is what I know leaks. The AC pod that open and shuts the center vents doesn't hold vacuum and I have the replacement diaphrams for all the pods under the dash. Just haven't pulled the dash out yet. I have tested all the doors individually. There is a very very small leak in the hatch lock (less than a 1" of vacuum in ten minutes). Which would seem to lead to the door locks not working properly after having sit for many many hours, but they don't work (well the passenger front and driver rear work sometimes) even while driving. I have tested the reservoir in the back, and it holds.

I have tested the shut-off valve by putting my mityvac on the valve itself and turning the car on, and then pumping the mityvac. The car shuts down after 1 to 2 pumps. I did find a little bit of oil on the ends of the plastic line going from the ignition to the shut-off valve. I pulled both of the lines connected to the ignition out of the car and looked at them. Niether of them seam to be full of gunk and oil. I cleaned the lines and replaced the rubber connectors again. Could the ignition itself be malfuncitoning?

I have checked the main line comming from the vac pump with the engine running. And it reads 22"-23" of vac. I have replaced the check valve on the doorlock system. I have replaced all the rubber connectors inside the car and in the engine compartment. I have checked the other check valves and they all hold.

So can the leaky climate control pods cause this much of an issue? Could leaky 3/2 valves in the tranny modulator cause these kinds of problems, and how can I test them to see if they are holding vac. All the other lines as far as I can tell are connected, although I have come across one or two that where disconnected, so things are getting better. Could my vacuum pump be bad eventhough it seems to be pulling the right amount of vac? Can a tiny leak in the door system cause the doorlock not to work, or are they just not getting enough vacuum do to other leaks. Any help would be great.

Thanks
Andrew

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I would disconnect the climate control and door locks. Plug with a golf tee and see how the car runs. Eliminate as many variables as you can. I have been finding my vacuum leaks by process of elimination. I have replaced many vacuum actuators for heat,door locks, and engine shut off. Its nice when the AC blows out the vents and not the defrost.

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2009 CLS550 55,000
2004 ML350 144,000
2004 X5 95,000
2002 X5 165,000
1996 320S 155,000 (sold)
1991 190E 192,000 (sold)
1989 300SE 160,00 (sold)
1984 300D 210,000 owned since 85, (sold)
1984 300SD 160,000 (sold)

Andrew,
Start your investigation in the engine compartment with a handful of golf tees.
Block off all bar one small vacuum ports (spider connector from vacuum line) with a golf tee. Put your Mityvac on the other small vacuum port. Start engine and measure vacuum. Stop engine and watch to endure vacuum does not fall more than 1" in 10 minutes (I may be a bit tight on this one) If it does, you have a problem with either the vacuum pump of brake booster. Fix that problem and continue.
Go for a drive to test the brakes. NOTE: shifting will be hard and late.
Do the brakes operate correctly?
If yes, continue, you have a good vacuum pump and brake booster.
Reconect the engine shutoff line to the spider. Does this make any difference.
Reconnect the vacuum line going to the transmission and vacuum control valve. This should allow smooth shifts at most speeds. If not, connect full vacuum to the modulator, this should give soft shifts and possibly flaring during shifts. If no vac shifts are hard and late and full vac shifts are soft, then the vacuum side of the tranny itself is fine.
Once the tranny vacuum is operating correctly, move to the central locking and check that.
Once the central locking is working well, only then, try the ACC. It is the least necessary vacuum controlled system on the vehicle.
Remember that the vacuum reservoir in the trunk may develop leaks also.

Take each step in sequence and you will find the leak(s) and you can then fix or defeat them.
Vacuum diagrams are linked in a "Sticky" at the top of each Forum page.
A similar thread has this post , which gives vacuum line colours for the central locking.
Have Fun.
Tony

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Tony from West Oz.
Fatmobile 3 84 300D 295kkm Silver grey/Blue int. 2 tank WVO - Recipient of TurboDesel engine.
Josephine '82 300D 390kkm White/Palamino int.
Elizabeth '81 280E, sporting a '79 300D engine.
Lucille '87 W124 300D non-turbo 6 cylinder OM603, Pearl Grey with light grey interior


Various parts cars including 280E, 230C & 300D in various states of disassembly.