Help with Vacuum Locks problem
 

Ok guys here is my question.

The locks on my new to me 85 300D have the following issues.

When I'm in the car and lock the driver door the driver rear door locks and so does the passenger front. The passenger side rear is dead. Yet when I get out of the car the key only locks the drivers door and the other 2 that are working will not lock with it. I assume I have a leak in the system because also the car does not shut off as smoothly as my previous diesel. It kinda shutters off. Where should I start guys? Thanks again.

Sounds like you may have a leak in your vacuum reservoir tank in the trunk of the car that stores vacuum for locking/unlocking the doors when the engine/vac pump aren't running. The tank is mounted up under the parcel shelf and looks like egg-crate. Check the connection where the vac line (I think it's yellow) goes into the tank. You may need to seal it up with some silicone if there's not a good seal there.

Another possibility is the leak that's causing your right rear door to malfunction is also the source of your reservoir leak when the engine is off.

Process of elimination
 

I would start by checking things in the engine bay:
1. Remove the lines coming off of the big black vacuum line that goes to the brake booster (mine has 2 T's) - plug one and hook up your vac guage to the other. Start the car and you should have 20+. If it fluctuates, it's probably you brake booster - if it's ok, keep looking.
2. Check the black box on top of the valve cover. Make sure those are tight.
3. Then, check all the connections where the vac lines go through the firewall.
3. Check the valve where one vac line splits in to two yellow lines and goes through firewall-you should be able to suck on the single end but not on the double end.
4. Under the drivers carpet is a cluster of vac lines. Two go to the passenger side and two stay on the driver side. (Green stripe unlocks-red stripe locks. Pull each one, one at a time, and test to see if they all hold vacuum. If one of the left side lines won't hold vacuum, check the rear driver door vacuum pod. If one of the passenger side lines won't hold vacuum, narrow it down by checking the lines that go to the front door, rear door and fuel door. Those connections are under both passenger side carpets and maybe in the trunk for the fuel door.
5. If all of those hold vacuum, your problem is, more than likely, a leaky connection at the ignition switch, the fuel shutoff valve or the vac reservoir.

Another test you can do while the car is running is to unhook the brown line that goes to the fuel shut off and hook up your mighty vac. The car should shut down within two pumps of the handle. If it doesn't, or if there is oil in that vac line, replace the shut off valve. Oil in the line indicates the integrity of the diaphragm has been jeopardized:D.

Also, I've had quite a bit of luck using zip-ties (some call them cable ties) to wrap around the rubber vac connectors and lock them down tight on the vac lines. It doesn't take much effort, and will still allow you to disconnect the lines by hand if you need to test them. I went through the entire car and did this to great success.

Get a mighty vac. It will make your life much easier.

I went through all of this a few months ago. There is a good color diagram on here somewhere. Probably in the vacuum troubleshooting section at the top of the Diesel Discussion.

Go, out under the hood and unplug the lines going to the yellow check valve and pull vacuum on the line to the vac. reservoir. If you have a leak there... Fixing the rest of the system is a moot point.

If you have a mighty vac report back your findings.

It is likely you have numerous other vacuum leaks in the A/C vacuum pods. But, worry about that later. You can isolate the A/C by plugging that line under the hood too.



EDIT: Here is the color diagram. Probably would not hurt to read the whole thread:
http://www.peachparts.com/shopforum/diesel-discussion/160169-w123-vacuum-interlock-diagram.html

No offense, but zip-ties on vacuum lines? Replacing the old rubber hose with new rubber hose doesn't cost much.

ur not the only one that sounded weird too

Fixed! The element in the truck was bad and the p.o just unplugged the element. I plugged the lines (while I wait to purchase a new trunk element ). And FIXED all the locks work now even when you shut down the car and it sits. Problem solved. Thanks guys.