Hey everyone, my name is David, this will be my first post... but I have been using this forum for a month or two now, I actually found the car I bought on here and I have been getting tons of information on here as well. I bought the car from redassag00 a few weeks ago.

I'm really happy about having this car, but that isn't to say a few problems have been annoying me.

The main annoyance is that my trunk lock won't turn.

I've been able to get into the trunk because the lock was in the horizontal position and I would simply unlock the driver's door to activate the vacuum at which point my trunk would unlock and I could simply push in the button and it would open right up.

Well, the reason this has annoyed me oh so much is because my vacuum leaks over night, so by the morning, I have no vacuum locks. In order to open the trunk in the morning, I must turn on the car and within 5-10 seconds everything unlocks.

Now I do plan on fixing the vacuum leak, but I would like my trunk lock to work as intended. I want to be able to turn the lock and press it in as it should, regardless of if the vacuum works or not.

So today, I took the trunk lock off just to see if taking if apart/putting it back would fix it. I was able to turn the lock after I removed the lock from the car, but only ONCE. Which means that now the lock is in the vertical position and stuck there!! Oh man, which means that now, the vacuum wouldn't even help me open it. I can still get into the trunk because I didn't screw the lock back on to the car yet.

Any ideas on how I can get the trunk to turn???

Sorry this post was so long, just wanted to give all info I could.

Thanks,
David

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1985 300D. 179,000 miles.

Are you using the square head key? The round head one won't work for the trunk and the glove box. It is the "valet" key so the valet can't get into your trunk or glove box. Over the years the locks just get full of crud. I pulled the one off my wife's wagon rear hatch and it had fine grit mixed in with the factory lube and I could hardly get the key in and out, forget about turning the lock. I pulled it all apart, cleaned it, lubed it with marine grease and put it back together and it works like new.

I am not positive about the sedans, but I think if the trunk lock cylinder is in the horizontal position it is always open, but I am not sure of that.

There are several posts about fixing the vacuum locks. Use the search function. You will also want to pick up a Mitevac for testing the vacuum system. It is also very handy for one man brake bleeding.

Welcome to the fold. If you are anything like me, you will get many hours of pleasure from driving and working on your Mercedes. As I slowly get my cars into shape I clean everywhere I work on the car so next time it will not be so dirty to work on. It makes it more fun to work on when you aren't getting covered in 20 + years of greasy dirt.

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Doug

1987 300TD x 3
2005 E320CDI

It is for sure the square head key, I can unlock and lock the glove box fine.

With this car at least, the horizontal position has allowed the vacuum to control the lock. It would lock when I would lock the driver's door and unlock when I'd unlock the driver's door. I got the impression that's how it was supposed to work, in fact, the manual for the car says that's how it's supposed to work.

I am going to fix the vacuum leak for sure, I am waiting for some parts to come in the mail, should come today I hope.

Hmm, when I remove the lock housing from the back of the car, how do I take it apart further to lube it up? I couldn't get mine apart any more than just removing the two nuts and unscrewing the part that connect the vacuum and popping it out the back of the car.

Thanks,
David

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1985 300D. 179,000 miles.

I have to say, I can't remember how to take the lock apart. It was simple enough though. If I can do it, you can too. Now that I recall, I could not even push the lock in to release it, but cleaning it and lubing it made it like new again. That is one of the best things about these cars, the quality of components is the best and many items are rebuildable instead of having to sink cash into parts.

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Doug

1987 300TD x 3
2005 E320CDI

So after fiddling some more, I was able to get it back to the horizontal position which makes my life easier for sure. I had to use a wrench to pull the black locking mechanism on the back of the lock while trying to turn the key in order to do it. I sprayed some lube on it, but it still won't budge with anything short of using a wrench and some strength.

I guess I just need to fix the vacuum leak then it will be less of an annoyance. I replaced the master vacuum switch today and the leak is less now for sure. I can lock and unlock more times before it runs out of vacuum power. I'm pretty sure there is a leak at the back driver's side door. Gotta check that out now.

Thanks,
David

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1985 300D. 179,000 miles.