Door lock issue - PeachParts Mercedes-Benz Forum

psaboic · #1 02-11-2015, 08:47 AM

Hi folks,

I'll be checking the vacuum system when I get the chance, but maybe you can point me in the right direction. My 83 300D suddenly developed a door lock issue. None of the vacuum operated locks work unless the car is running. No other vacuum issues (shifts fine, shuts off normal, brakes normal) just the locks will not open or close unless the car is running. I'm thinking leak at the reservoir, or the line, because of the fact I can shut the car off and try to lock the doors within 10 seconds of shutting it off and nothing, but start it back up and the locks work fine.

Any ideas

Thanks

leathermang · #2 02-11-2015, 08:54 AM

There are schematics of the vacuum lines online... somewhere.... make a list of all your vacuum items which do work....and do not...
then look at the schematic.... and see what areas are shared by those which do not work... or are sharing a one way inline valve perhaps.... this is like electricity in that it is like a tree... you keep going down the limbs which are dieing until you find a common branch....and look for problem there...

rscurtis · #3 02-11-2015, 09:40 AM

Check the 4-way connector near the oil filter. They can get brittle with age and leak, even though the part looks OK.

Phillytwotank · #4 02-11-2015, 11:45 AM

I'm thinking... goodly leak in the Door lock "circuit". My guess would be between under the hood and the main valve in the drivers door. Do you have a midyvac?

Diesel911 · #5 02-11-2015, 01:00 PM

Over on Benzworld.org there is a Member Uberwasser that had a good trouble shooting theard.
Assuming the either 2 or one Check Valve with 2 Vacuum lines going to it right at the Fire Wall are working you leak has to be in the interior of the Car unless there is some issue with the Rubber Tubes on the Check Valve.
The Check Valve/s are supposed to trap the Vacuum in the locking system.

Checking the Vacuum Lock system seems harder then it is. Start of by removing the Door Panel and you will see a Vacuum Valve connected to the Door Lock Linkages. That Vacuum Valve can be the source of the leak and after that it is generally one of the Lock Actuators.
There is 3 Connectors on the Valve. One for the Vacuum Supply and then one for the Right side of the Door Lock System and one for the Left Side of the Door Lock System. The Right side includes the Trun and Fuel Fill Cap Cover in the System.

Not sure who to thank for the Diagram but I believe the Color matches the colored Strip or color on the Vacuum Tubing.

So with your hand Held Vacuum Tester (Mighty Vac) you can yank off one of the Vacuum Hoses and test to find if it is the left or rignt. I can't remembe which part has the Vacuum Res. however that not normally where the Problem is.

I was also supprised to find that the Rubber Tube (you can use Vacuum Hose if you have to replace any) were all in like new condition not at all rotted out like I thought they would be.

Also the Plastic Vacuum Tubes are color coded.

shertex · #6 02-11-2015, 03:07 PM

My 84 does exactly the same thing. I concluded that it's a leak in the reservoir of the line to it.