cannot lock/unlock via driver's side door - PeachParts Mercedes-Benz Forum

Tanksowner · #1 12-30-2010, 07:40 AM

The vacuum lines are fine, but the key won't turn back and forth in the driver's side slot to lock or unlock the car. Has anyone experienced this before? What did you do to fix it?

EDIT: None of the plungers will go down.

Hi there

By request from another member, I'm posting the solution I found with the door lock issue.

Yesterday, the issue I had was not being able to lock any of the door locks manually, or by using the vacuum system on the driver's side lock. Essentially, the key wouldn't turn at all. I tried opening the other doors and found that I could pump the passenger side plunger, which I think loosened up a frozen vacuum line. Afterwards, I tried locking the doors again via vacuum, and it worked! I had gotten the car washed yesterday, so I'm not sure if some water got inside and froze up, blocking the airway. But either way, that was the solution I found.

vstech · #2 12-30-2010, 11:58 AM

sorry, but could you post here what you found and what the solution was?

okyoureabeast · #3 12-30-2010, 12:16 PM

Is the lock frozen?

Can you lock the vehicle from inside by pushing the lock down?

nevremj · #4 12-30-2010, 12:30 PM

I had the same problem in an 85 300d.

It turned out to be coagulated dust, dirt etc, possible bound up with WD40 from previous owner. I started to take the lock out, but I exposed enough of the lock to get it lubricated properly (I used silicone spray) and that seemed to fix the problem.

toomany MBZ · #5 12-30-2010, 02:14 PM

^ Good advice.

If that doesn't work, it's possible to have an air lock, you'll need to open a line somewhere to the atmosphere to vent the system.

vstech · #6 12-31-2010, 11:26 AM

it's best to add solutions to the original post. creating new threads with only the solution in it, make it difficult to find in a search for problems.
thanks for the solution you found.
I merged the threads.

tyl604 · #7 12-31-2010, 03:27 PM

I had the problem in my 81 300SD. It turned out that the driver's door locking mechanism - the part with a sliding rod- had suffered a small broken plastic holder or holder or something (it was a long time ago). It would not move up or down and that is why the door would not lock any more. In any event by taking off the door panel, you could just look at it and figure out the problem. Seems like I just bent it a bit so it slipped back into the plastic holder. Has worked now for about another 8-10 years.

Now that I think about it I believe I did a post on it; I will look.

tyl604 · #8 12-31-2010, 03:32 PM

Found my old post. Hope this helps. My earlier post comments were not exactly correct.

For about a year now my key would lock the doors but would not unlock the drivers side; I had to unlock the passenger side door and climb across the front seat to unlock the driver's door. Pretty embarassing.

Thought it was the tumblers in the door lock so I removed the lock this weekend. Took it to a locksmith; he turned the key back and forth in the lockset and said there was nothing wrong with the tumblers and that the lockset was working fine. Headed back home.

Finally saw that the unlocking mechanism is a plastic piece which goes through a hole in a metal flange; when you turn the key, the plastic pulls the flange and the door unlocks. Over the years the plastic had worn down some and it slipped out of the hole. I just bent the flange back a little and reinserted the plastic in the hole and it works again. Cost - zero.

Hope this helps someone out there who thinks he might need to buy a new lock.

sd300td · #9 01-02-2011, 12:48 PM

My 240D just came down with this illness. Key does not turn in the driver's door lock. Vacuum locks work fine. I suspect gunk build up and worse so will attempt to clean and relube.

Shamed to admit it, but I actually grabbed the wrong can while I had the door card off for vacuum related repairs. I lubed all the mechanisms and linkages in the doors while everything was apart. Unfortunately, I accidentally grabbed the can of spray adhesive rather than white lithium grease and gave the lock mechanism a good spray...

So, a related topic would be: what's good at removing/dissolving spray adhesive??

vstech · #10 01-02-2011, 01:09 PM

!!!
what kind of adhesive? look at the can. likely the majority of it will just fall off the already somewhat greasy slides when it dries.
for the lock, I've had good luck using brake cleaner spray and eliminate ALL traces of any type of lubricant in there. blow out well with compressed air, and the key works great.

sd300td · #11 01-02-2011, 03:28 PM

Quote:

Originally Posted by vstech

!!!
what kind of adhesive? look at the can. likely the majority of it will just fall off the already somewhat greasy slides when it dries.
for the lock, I've had good luck using brake cleaner spray and eliminate ALL traces of any type of lubricant in there. blow out well with compressed air, and the key works great.

Just your basic spray adhesive from Pepboys, etc. I use it to reglue the vapor barrier, which is why I had it out of the cabinet. I grabbed the wrong can as the lubricant was right next to it. It wasn't the strong 3M stuff...

I just gave the lock a good dose of wd-40 and it freed it up. Eventually I suspect that it'll need some proper lube. Is white lithium a good choice? Or should I use some moly-b grease, or ???