Help My Trunk Won't Open - PeachParts Mercedes-Benz Forum

bluebird · #1 01-17-2008, 07:56 PM

1984 300SD key turns but button will not push in. All doors are unlocked, as well as the fuel filler flap and with the key inserted into the trunk lock, the key will turn but the button will not push in. Help I really need to get into the trunk. I have searched the forum but alas no luck.

matthias08 · #2 01-17-2008, 07:59 PM

you could be like a friend of mine w/ an SDL and smash the drivers side tail light to get in... seriously... it was a horrible sight.

JimSmith · #3 01-17-2008, 08:11 PM

First, your location is listed as Washington State, and there are some parts of Washington State where this time of year it gets cold enough that the lock could be frozen. If that is the case, try heating the button with a cigarette lighter, or squirting it with de-icing juice. If you are not in an area where freezing is possibly the problem, try a few more things.

If the button won't go in at all try turning the key the other direction, and, with the key still in the lock, try pushing the button in.

If nothing works and the button doesn't go in at all, try squirting some WD-40 or the like into the locking mechanism and on the outside surfaces of the button up where they go into the lock. Same with the key. Then make sure the key is turning the lock. It cannot be the round headed key. It has to be the square headed key. I believe the key stops at a 45 degree angle to horizontal when you are supposed to push the key and button in together.

If all else fails, use a wooden block to protect the button and your key, and then rap on the button through the wooden block with a hammer. Seems something is stuck. I have seen the key part of the lock stick pretty good before, where it wouldn't turn, or turned very hard and didn't make it all the way to unlocking. The answer was to muscle it.

For what it is worth, the button should always go in - when the lock is engaged the button going in just doesn't do anything. The button staying out is a sign something is jammed or dirty or otherwise mechanically unhappy. Maybe someone tried to break in and jammed the works?

Good luck, and be careful. Jim

niki716 · #4 01-17-2008, 08:31 PM

The central locking system doesn't work on my car--and the trunk no longer opens. i figure when i fix the vacuum leak, that'll fix the trunk lock. I'm having the same problem you describe: key turns, but no pop to the button--so maybe it's not the vacuum leak, but a coincedental mechanical problem. Can you please let us know what worked?

JimSmith · #5 01-17-2008, 09:04 PM

The vacuum system should only affect the vacuum operated functions, like when one door lock or the trunk lock is changed it "communicates" this change of state (locked or unlocked) to the other locks. It does not affect the key function. Turning the key in one direction "synchronizes" the trunk with the vacuum system, while turning it in the other direction makes it operate only with the key, and the key has to stay in the button, turned against a spring load while the button is pushed in. The first bit of button travel is "free" meaning it does nothing, then you can feel resistance and pushing it further opens the lock. Jim

charmalu · #6 01-18-2008, 02:06 AM

If all else fails, try this. I think this for a w123, but who knows?

www.peachparts.com/shopforum/showthread.php?t=194141

Charlie

TX76513 · #7 01-18-2008, 08:24 AM

When you get in your trunk and replace the lock - you will most likely see that the only plastic piece on the trunk lock has failed. It's a small black plastic cog. Been there X2 now. I personally consider this to be an pre-engineered failure.

bluebird · #8 01-18-2008, 11:48 AM

Here is a thread I found on another forum for a W123 and I don't know if this also applies to a W126. W123's apparently (some) have an emergency trunk release cable I know W126's do not have this. Triple Dammmm. What to do next?
Trunk Lock Mechanism

I have figured it out!!!!

It took 3 people and about 2 minutes.

1 person had the key turned in the trunk cylinder and trying to push in the lock.

1 person was pulling up on the trunk.

and 1 person (myself) was repetedly pulling on the emergency trunk release (with a bar in the loop to assist!) under the rear seat on the driver's side.

The trunk OPENED!

This is what happened...

The emergency trunk release pulls a metal plate away from the key cylinder which then allows the cylinder to be pushed in. The key turned "15 minutes" counter clockwise and being pushed in allows the trunk latch to pull back and the trunk can then be pulled up (opened).

There is an electronic solinoid-like box that is connected to the same metal plate as the emergency trunk release cable. This solinoid has 2 small springs (one pulls towards the cylinder and one pulls away depending on the postintion of the solinoid) and a 3 wire electrical connection to it. My solinoid is stuck in the postion which "pulls" the metal plate towards the cylinder, thus blocking the cylinder from being able to be pushed in whether you have the key or not, or wether your vacuum lock actuator is working or not. The emergency release cable either streches or the brass clamps on the cable loosen over time, thus making it difficult to open the trunk with only one person pulling the cable. You need another lifting the trunk, and if your vacuum actuator is out of air (leaking) or not working at all, you need another person keeping the key turned "15 mintues" counter clockwise and pushing in on the key cylinder. It took about 3 minutes of coordination and the trunk finally opened.

TO FIX THE PROBLEM, I simply removed the spring which pulled the plate towads the cylinder and attached the other spring to the far side of the plate which then pulled the metal plate away from the cylinder perminately. (if the solinoid decides to start working again it is ok because it only means that the spring will have less load on it.) My trunk still locks fine when I lock all my doors due to the vacuum actuator still operating (well it leaks out over time but when it locks it stays locked!) Now my trunk cylinder pushes in all the time and when I unlock the doors and it can be opened, or when the doors are locked the trunk is locked and I must insert the key, turn it counter clock wise "15 minutes" (1/4 turn) and push in the cylinder and the trunk can be opened just fine.

I wil be uploading pictures as soon as the rain stops in Farmington NM!!!

I also have good info on the hazard / flasher / instrument relay I will post next!

Thanks for all your help!!!
Last edited by exmind : 03-24-2007 at 04:40 AM.

bluebird · #9 01-19-2008, 12:29 AM

OK, here is what has transpired.

Unlocked the driver’s door on a 1984 300SD, all doors including the fuel filler door unlocked. However the trunk button would not push in to open the trunk the key slot was in the horizontal position. I put the key into the trunk lock and turned it counter clockwise and still the button would not push in.
Took out the rear seat and seat back, removed the First Aid Kit latches, lifted up the package shelf and removed the plastic tray.
Took flash light and looked into the trunk to see if my tool box had rolled and obstructed the latch. Couldn’t happen the whole latch system is well protected. Too well protected. Using brute force isn’t what was necessary. You could not get at the lock mechanism with any sort of device as it is covered up with a pretty sturdy carpet.
Went to Seattle to see Rob at Benz Friendz to see if he could enlighten me. Response was YOUR SCREWED, unless you want to drill into the body sheet metal and the lock mechanism and then insert a piece of stiff round metal an pop the lock or brake out a tail light assembly.
I went back to the car to retrieve the lock assembly parts out of my parts 300SD so he could show me what he meant. He had shown me on a car that had the carpet removed but I couldn’t see exactly what the process was.
I unlocked the PASSENGERS DOOR with the key and unlocked the back passenger’s door to get the parts. Grabbed the parts and started back then changed my mind and decided to try the Trunk button once again, I had left the passengers side unlocked.
THE DAMNED THING OPENED!
Locked the car from the passengers side tried the trunk and it was also locked tried to unlock it with the key and it opened. Did this process several times and it continued to work.
Told Rob and he said you bring it to the Doctor and things will sometimes self heal. Go Figure.
Thank you all for all your suggestions.

Mark DiSilvestro · #10 01-19-2008, 09:48 AM

Well, I had a problem last year when I decided to see why my '81 240D's vacuum locks didn't work. I left the motor running and the driver's window open (just in case) while I messed around with some disconnected & plugged underhood vacuum lines. Reconnected a couple, pressed down the driver's doorlock button and Voila! All the locks locked. Pulled up the button but no Voila this time. So I could still get into the car but now the trunk was permanently locked. Did I mention that the PO had changed some of the locks so the trunk now used a separate key, which I didn't have!
After tracing the vacuum lines under the carpets, I found the door and trunk vacuum connectors under the passenger seat. After some experimenting I figured out which lines went to the doors and the trunk, then disconnected the trunk lines and plugged the rubber tees. Now I had door locks that locked and unlocked, but still no way into the trunk. (and unaware there migt be an emergency trunk release) I figured out that, while obviously the locking part of the trunk's vacuum motor still worked, the unlocking side must be shot. Fortunately, I happen to have a Mighty-Vac hand-pump and I decided that if VACUUM couldn't work the damaged unlocking side of the vacuum motor, maybe PRESSURE could operate the locking side of the vacuum motor IN REVERSE to make it unlock the trunk. Voila! Trunk unlocked. And I've since obtained the proper key, so I won't need to dig around under the carpet next time the trunk gets locked.

Happy Motoring, Mark

bluebird · #11 01-19-2008, 12:09 PM

Emergency Trunk Release???
When the weather and time permits I will figure a way to put in an emergency release system somehow someway. I spent 1 1/2 days on this pesky problem. I run on WVO with a 6 gal boat tank in the trunk ( no guage except on the tank ) for diesel. Starting and stopping is what I use that for so I had no way of knowing what was left in there. Does anyone know of any Emergency Trunk Release mechanisms that would work for this application, if so diagrams or pics would be really helpful.

Lycoming-8 · #12 01-20-2008, 03:01 AM

Isn't the solenoid, that was pulling the plate over and blocking the trunk latch button, a part of the MB alarm system installed in a number of the later W123's & W126's? If so can 't the alarm be defeated, which would then keep the solenoid from operating?

JackG · #13 01-20-2008, 05:37 AM

This is another emergency situation remeady for getting in the trunk.
Surf and Turf showed me this one on his one parts car with no damage caused whatsoever.
needed:
1)a block of wood approx. the height of the trunk(2x4, 4x4, whatever)

2)one 2x4 approx 3-4 feet long to pry with

3) 1 B.F.H

4) small block of wood to protect lock from BFH

Set the block of wood up with the pry bar(2x4) under the lip of the truck lid. have someone apply constant pressure with this while a second person holds the small block on the lock. Third person hits small block with BFH. Start with light tap and get progressively harder until lock pops open.

Caution.....DON'T MISS

I saw this done and it does work very well.