1980 300D Door Locks - PeachParts Mercedes-Benz Forum

#1 05-06-2002, 09:31 PM

Greetings !
I am new to this site, and new to MB also.
I recently aquired my 1980 300D. If seems to be a solid car however I am finding its quirks. I think I have a vacuum problem, but one thing that I am stummped about is the door locks. I cannot get them to move up or down. This is on all the doors.
I have not removed the door panels yet, I would like some feed back before I jumo into it. I have the Mighty Vac tester & guage and I am ready for action.

Robert

#2 05-06-2002, 09:37 PM

Stuck locks are almost certainly a vacuum problem. Just get going with the MityVac--there's no shortcut. Check all lines.

euro 287 · #3 05-06-2002, 10:08 PM

Go underneath hood and look towards the bulk of vacuum lines on the drivers side firewall. You will see a couple of big yellow lines that connect to a check valve. One is for resevoir and the other is supply. Easyest way to do this is disconnect both , unlock doors with key from outside car, now pump one up until door locks try to move, that is supply. To ck the resevoir you will have to pump along time on the other one. Now if you have found supply and the door locks try to move but dont hold vacuum in lock or unlock its time to go to check points. On the drivers front seat pull up the carpet panel, on your left you will see a black cover, pull it up.
You will see red vacuum lines and green .Green are unlock and red are lock. Now connect the mityvac to one ( probably going to rear or drivers rear door) . Check these and see if they dont hold. You can watch the rear door and watch the lock try to move. Now if the vacuum lines going to the passenger side leak then do the same thing on the passengers side checkpoint. If all are ok and the passengers side going to the trunk still leaks then you can go inside the trunk and gain access at the gas flap actuator and check the trunk lock actuator and gas flap. Sorry so long , hope this helps.

tcane · #4 05-06-2002, 10:57 PM

In addition to euro287's excellent info, I'll add that there are diaphragms in the door, trunk, and gas flap that will probably be the problem (of course, it can be leak in the vacuum line or fitting but not common). The diaphragms can be bought separately to rebuild the bad components. I had to rebuild all of mine over a period of a few months as the other diaphragms began to leak. Pretty easy to rebuild, the pain is getting the door panels off without damaging anything. There is special tool that is flat on one end in a U shape that is inserted between the door panel and the metal portion of the door and used to pry the panel retaining pins out of the door. There are several of these pins (as I recall 8 or so) and you use the tool at each pin. Unscrew the push button for the door lock. Also, the door pockets connected to the door panles (if you have these) have a plastic hook into the metal portion of the door, the hook is located on the upper front of the pocket. Once the door panel is loose carefully pull the panel and pocket backward to release the hook. It is easy to break the hook if you are not careful. Once the panels are off you'll find the lock diaphragms at the bottom of the door, just follow the rod connected to the push button lock down to the valve.

Good Luck!
Tom

#5 05-06-2002, 11:13 PM

Thanks for the great info & keep it coming !
Any soruces for the door panel tool & the lock diaphrams ?

tcane · #6 05-06-2002, 11:28 PM

Forgot to mention that you'll need to unscrew a few things before doing anything else on the door panels: the arm rests have two #3 phillips head screws, the chrome pieces surrounding the lock mechanism, and the unlatching lever has a small phillips screw underneath the black plastic liner behind the latch. Carefully pry the plastic liner out with a small flat blade screw driver to reveal the phillips head screw.

Also, there is a plastic liner between the panel and the metal part of the door - this is a moisture barrier and needs to be in place. If damaged, either fix with tape or make a replacement out of a large trash bag. Otherwise, water will ruin the door panel.

Here at FastLane you can order the diaphragms and maybe the tool. My tool is Snap-On, but you may be able to find one at a local auto parts store (NAPA has lots of tools, Pep Boys, Auto Zone, O'Reillys, etc.), make some calls to find one.

Good Luck!
Tom