I went to spend the night a my moms house last night as she just got out of the hospital. I put my overnight bag in the trunk and drove over. When I got there the trunk would not open. All 4 doors lock and unlock fine. On the way I made one stop and locked the car up. I have the trunk set so it locks and unlocks with the doors. Its never had a problem before. I have tried a million times with the key but it won't turn or pop open. I called my roadside assistance service and the called a locksmith but he told me he wouldn't be able to get into the trunk without damaging it.

I've read about a cable under the back seat. Is this in all models? How do you get the backseat out? Will this release the trunk? My main keys are in that bag and my work keys. Is there a way to access the trunk inside the car (from behind the rear seat) ? I probably will drop my car off at my mechanic up the road from me in the AM.

Not on a 1980 300D. Have you tried cycling the door locks with the engine running?

You mean locking and unlocking the doors with the key while it is running? I tried it but nothing happened other than the door locks working, trunk didn't budge.

I think qwerty meant try unlocking the door with the key while the engine is running...creating better vacuum hence a better chance of cycling the trunk lock... is that right q?

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"Those that turn their guns into plows shall serve and tarry for those who do not." Thomas Jefferson

You can access the trunk to retrieve your smaller belongings by removing the first aid kit tray. Its only attached by two little screws.

I've seen someone pick a similar Mercedes lock on a W126. It took him about 15 minutes and he destroyed the lock in the process.

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1985 500SL Euro w/ AMG bits 130k
1984 300SD Turbodiesel 192k
1980 240D Stick China 188k
2001 CLK55 AMG 101k
2007 S600 Biturbo 149k Overheated Project, IT'S ALIVE!!!

Make a jiggler and jiggle the trunk lock open.

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Have you ever noticed that anybody driving slower than you is an idiot, and anyone going faster than you is a maniac?

As long as they would add one additional commandment for you to keep thy religion to thyself.
George Carlin (Wonder where he is now..)

1981 240d (engine donor 1983 240d) recently rebuilt engine hurray! - No more.. fought a tree and the tree won.

pearl black 1983 240d 4speed (Converted!@$$%) atleast the tranny was rebuilt.

Actually 1985 and possibly 1984 300D's that are equipped with the alarm system do have the trunk latch emergency cable located under the rear seat cushion. Our 1985 parts car has alarm system and the cable. Have seriously thought about trying to move it to the 1983 in case I run into an issue as posted here. Pull out or push in on the little orange clips at the bottom of the rear seat cushion and it will lift out very easily.

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1961 190Db retired
1968 220D/8 325,000
1983 300D 164,150

I would try this as it has worked on my 79 116 sd before.
Unlock all the doors using the key in the drivers door.Get in the car
and drive the piss out of it for a bit.Then try the trunk again.

I have a similiar issue on Coda, my daily driver. If I know I am going to be opening the trunk when I turn off the engine; I will lock the doors from the inside while still driving by pushing down the driver door lock "button". Then I will unlock it, before stopping. It hasn't failed me yet.

In addition, if parked in the driveway with the engine off, I just get in the car, push the driver door button down. Then pull it up. This has not failed me yet, either.

Obviously I have an issue with the trunk lock mechanism, but no vacuum leak in the system elsewhere.


Does your fuel door lock and unlock with the doors?
Another idea for your 300D, might be to find the vacuum hose that goes to the trunk (and fuel door) under the passenger door mat near the seat, outside corner. If you sit in the passenger front seat and have your knees at 90 degree angle, the connections should be to the outside of your right heel. Hook up a Mity Vac to the hose and give it a LOT of vacuum.

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daw_two
Germantown, TN

Links:
Sold last car --- 05/2012 1984 300D Light Ivory, Red interior
No longer selling Cluster Needles Paint
No longer selling New Old Stock (NOS) parts

Past:
3/2008 1986 300SDL "Coda"
04/2010 1965 190D(c) "Ben"
& many more

Are we talking about a W123 300D or a W124 300D?

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91 350SD
14 F150 Eco
19 Fusion Hybrid
11 GT500

Yes, the idea was to improve the vacuum level. It would not matter if the key was used or the knob was pulled.

The OP's profile suggests W123.

On my 1985 300D Turbo, the trunk lock is apparently operated by both vacuum and electric. About 3 years ago the trunk vacuum valve was leaking, so I just plugged the vacuum line there. It can still be locked and unlocked with the key.


David
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1985 300D Turbo

You should check out the 'How to break into a stuck trunk without breaking anything' thread. It has a very good description with pictures on reaching through the first aid kit hole to pop the latch from the inside.

Breaking into 123 trunk w/o breaking anything

Functional Diagram Central Interlock you can download from zSHARE
80-900.pdf - 0.22MB

Looks like I'll be getting familiar with it too as I tried turning my key counterclockwise 150 degrees or so rather than the normal 60 degrees in the trunk lock and now I can't open mine either.
Autozone has the plastic MityVac for $30 which seems to work fine.

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1985 300D Turbo
"Evolution is God's way of giving upgrades" Francis Collins

Hey i might have a reallllllly nice trick for all of you guys!!!! i have done this 25 or 26 times on 20 different M-B's and it always worked! (to get lock's unlocked) first get a foot tire pumping machine "to make sure you do not use too much pressure to break the actuator's!!!) and take off the right rear passenger door panel, now disconnect the vacuum hose from the actuator, now plug in the tire pump to the vacuum hose and pump the foot tire pump.

Now you should get pressure in the system that will unlock everything BUT, not too much pressure so it does not break the actuator's or create a leak or something. i have done this on 20 different car and even 5 times during -20 weather and it worked! you should be able to make it work!

I hope this helped anybody to get their M-B opened up!

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1991 560SEL AMG "Jap spec"
1989 560SEL Euro spec