Hi All,

Last week, my power door locks stopped working and shutting off the engine with the key has stopped working about 80% of the time.

I have verified the vacuum pump is producing vacuum and my vacuum reservoir can store it. The yellow check valve at the firewall is holding pressure, however the yellow line that connects to it does not store any pressure.

On the driver's side vacuum lines, the front yellow-green slowly looses pressure and the front yellow-red does not hold pressure. Two of the three rear lines do not hold pressure.

On the passenger side, I am able to pump up the passenger door and rear right door and release them. Both hold pressure good. However, the rear yellow-red line that connects towards the driver's side and the rear yellow-green do not hold pressure.

I'm obviously not an expert on this, but it appears I likely have at least two issues here -- one that is preventing the shutoff of the engine and another that is causing the door locks to not work. I think the more likely scenario since everything worked perfectly until a week ago is that I have a longer-standing slow leak on the inside and a more substantial problem on the supply line. My understanding is that a leak on the doors in the cabin would likely not cause a problem with engine shutoff because the engine shutoff valve is directly connected to the main supply line that connects to the brake booster.

My question is where the yellow line that connects to the yellow check valve goes when it disappears through the firewall and whether it connects up to the front lines on my driver's side that are not holding vacuum.

Thanks,

Dkr.

The year and model would be great to help you.

__________________
1985 300D 198K sold
1982 300D 202K
1989 300E 125K
1992 940T

"If you dont have time to do it safely, you dont have time to do it"

"The democracy will cease to exist when you take away from those who are willing to work and give to those who would not."

Sorry, it's a 1984 300D.

Dkr.

Well, it looks like I may have found the next thing to look at.

On the Peachparts diagram, I originally mis-read the colors.

http://www.peachparts.com/shopforum/attachments/diesel-discussion/75556d1261592167-w123-vacuum-interlock-diagram-w123vacdoorlockdiag_cghj564684.jpg

It appears that plain yellow disappears behind the firewall behind the instrument panel to the driver's master key vacuum switch. Is this the master lock on the driver's door panel or something behind the instrument panel that then goes down under the driver's seat and then into the driver's door?

Thanks,

Dkr.

I have the same car. It has a very elaborate vacuum system which was resulting in a variety of symptoms. I found it very helpful to simplify things where I could (like get rid of EGR). When I was done, I had everything working perfectly, except door locking/unlocking with engine off (there's a leak in the reservoir).

__________________
14 E250 Bluetec "Sinclair", Palladium Silver on Black, 153k miles
06 E320 CDI "Rutherford", Black on Tan, 171k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver, 142k mi, wastegate conversion

19 Honda CR-V EX 61k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife

The illustration tells me that line goes to a single orifice check valve, then the lock itself.

As a test, you may want to plug off the line going to the yellow check valve under hood, then try to shut the engine off. I have disabled the door lock system on the coupe.

__________________
83 SD

84 CD

Yeah, I think that's par for the course. Prior to this, I was fortunate to be vacuum problem-free for about a year and a half now...

Dkr.

I have a Federal 84 300D and also faced finding a leak.

At first it seeems complicated but basically as the other Member siad where the Tubing goes through the Fire Wall you disconnect one Line and plug off the vacuum Side. If you Vacuum Issue improves or goes away then you know that particular part of the Vacuum System has a leak some place in it.
Do that to the other Vacuum Lines eacept the solid black Line which is a Vent.
If you have a Blue Lint that goes to some sort of adjustment in the Seat; mine does not have that.

If it turns out be the locking system you first check the main Valve at the Door behind the Door Panel. That is one of the typical causes of a leak. You see 2 lines connected to it. One is the Vacuum Souce and one is locking and the other is unlocking Vacuum.

I was supriszed to find that the Rubber Vaccuum Line Connectors all looked as if they are new unlike the under the Hood Connectors.

I followed the Manual and it has you removing the Drivers Door Thresh hold to get at the V Lines under it and you use you Might Vac to test there and you can eventually narrow down what was in My case a bad Door Actuator.

Under the Hood the typical vacuum leaks are caused by cracked rotted rubber connectors and you can often see that by handeling the lines and visually inspecting the connector.
If you have the little Plasticl Valves on the Valve Cover the levers wear and the Valves can leak because then pop out too far and I guess they can simply leak from wear. Again disconnecting that part of the Vacuum Circuit and pugging the Vacuum supply end is the way to troubleshoot.

Think of that colored Vacuum Diagram as a Map. You start of on the Main Street and test and work your way to the smaller streets using your Mighty Vac/Hand Held Vacuum tester.

__________________
84 300D, 82 Volvo 244Gl Diesel

I did some more work on it today. The notable things are that I found exactly where the engine shutoff valve connects and tested it and I was able to shut down the engine with my mity-vac. The brown/blue line that connected to it however does not hold pressure. My understanding is that this line connects to the ignition switch so I should be able to pull it off there and turn the engine off from behind the instrument panel with my mity-vac. If I can do that, then the next step is to check the valve connected to the ignition switch.

Also, the yellow line that does not hold vacuum apparently is in my driver's door, so I'm going to pull that apart tomorrow and make sure it can hold vacuum.

Dkr.

It is typical for the rubber diaphrams inside the doors vacuum pods to degrade. There are vacuum pods for the trunk and fuel door also.
Someone on the forum makes replacement rubber diaphrams for a fraction of the cost of a new pod. Charlie (charmalu) may have the info for that member if he still makes them.

Blocking off the lines to the yellow check valve
with a golf tee is what most do. (door locks)

My locks seem to work better in the summer after the car sits in the sun a bit.

Thanks, my right side are both working and holding pressure. I don't use the power lock on the trunk (although I wonder if that affects the rest of the vacuum system). AFIK, all of the W123s I have had have had leakage on the fuel door, but it doesn't affect too much.

Dkr.

I would plug up the feed the lines leading to the locking system. Then you can see if your shut down works. My hunch is it will work.
But if it doesn't, than it could be the climate control vacuum system is leaking and you would plug that feed line and try it again.
If I am not mistaken, the ignition switch should be the only item using vacuum besides the brake booster. If that doesn't work, then it's the ignition or the brake booster.

But reading what you are saying, I am guessing the leak is coming from one of the left doors.

.

__________________
1983 123.133 California
- GreaseCar Veg System

Well, I tried quite a bit to get the driver's door card off today. I've taken at least a dozen of these off and I know how to lift it so as not to break the map pocket. However, this one is absolutely stuck on the map pocket. As I try to lift up, it simply won't budge and I know if I give it some more force it will snap the plastic fitting. I even tried to spray some penetrating oil in there but it isn't moving. I suspect it has never been removed since it came from the factory. I'm putting it back together and will see if I can find any tricks that I don't know about on it.

I ordered an instrument panel removal tool which should be here Monday. I know how to push it out from the bottom but I figured I've removed it enough times to start using the proper tool.

Dkr.

How are the brakes? They use vacuume also. Try the previous post suggestions first.


Just an idea for later:
Brake booster has a seal between the booster and the fluid resivoir, its really cheap to replace...better than the cost of the booster

Brakes are running great, transmission shifts perfect and A/C is working.

Dkr.