how to get into trunk with no key... W201
 

My 87 190D 2.5T broke the key, and it's not the original trunk lock, so MB as a source of savior is out...

I figure I'll need to get the unlock function to work... I've always needed to use the key to open the trunk, my plan was to get the vin matched lock installed after I get the car back on the road... but I just broke the key tonight, and it was my only one. HELP ME! it's not critical or anything, as I've already removed everything from the trunk, but I'll need in there at some point, so making plans now to get it unlocked, so I can change the lock!
thanks!

If it is like the 124 it should have the bi-directional vacuum/pressure system for lock and unlock. Driven off the auxiliary pump that is either under the back seat or in the trunk.

The actuators have one yellow hose that has either vacuum or pressure on it. I cannot remember at the moment which mode (vacuum or pressure) causes which mode (locked or unlocked). I think all the actuator pods are all teed together from the same line for the doors, trunk, and fuel flap.

Unless you turned the key in the trunk lock to the "permanently locked" mode, you should be able to unlock the passenger compartment, freeing the trunk mechanism to the "unlocked mode" and that should allow you to push the button in to open the trunk.

The vacuum pump is under the rear seat bottom passenger side. If the vacuum actuator for the trunk lock is good then you should be able to do as jay_bob has described.

If the actuator is not right and/or the lock is in the permanent lock posision then it will be more challenging. Basically have to reach into the trunk from the first aid box and grab the lock mechanism with extra long needle nose pliers and pull the lock to the unlocked posision.

If you can obtain any other 201 trunk lock mechanism with a key that can operate it you can disassemble the lock cylinder and very easily rearrange the cylinder leaves to match your ignition and door key. You might even be able to do that if the key is broken off in the lock where it allows the lock cylinder to be turned.

If you can't get the vacuum operator to reverse it's position it is connected to the lock mechanism on the passenger side, it's a rod about 6" long. It needs to be pushed into it's - facing the trunk - left most position where it allows and the lock mechanism sear to release the latch fork when the button is pushed all the way in.

It would be quite hard to reach that rod from the hat shelf, I'd bet sacrificing the passenger tail light will be the most efficient route. And if for some reason you still can't get the lock to release, the lock receiver bolted to the trunk that the latch fork secures into can be removed and then the trunk would open and you could remove the lock mechanism from the trunk lid and figure out why it won't unlock. You just need to pry the plastic trunk liner away from the trunk's rear wall where it covers those two 8 mm bolts. Or there are two 8 mm bolts that attach the lock mechanism to the trunk lid, but they may be harder to get at with the trunk latched and you'd have to get the vacuum operator rod disconnected also, and then wiggle that all out.

I have a spare 190D 2.5T vehicle to play with that has a working trunk, so at least I'll be able to open that trunk, and see what does what before I attempt it on the bad one, but UGH... broke my only key... UGH.

If the key is still in the lock, you can have a locksmith get it back out. They he can get you keyed back in. They aren't real cheap for a service call, but it can eliminate forcing your way in.

no, the key broke on my keychain while it was attached to my belt loop... no idea how it broke, I may have slammed a door on it, or cought it in my tractor moving things around in the yard.

I had to get into my SD by busting the tail light, so I would do what Obamalamadingdong suggested. You can then get inside with a 10mm wrench and remove the part on the trunk lid.
http://www.peachparts.com/shopforum/diesel-discussion/317472-1984-300sd-w126-trunk-wont-open-even-key.html

If it has the same layout as the early 300D's, this may work:

http://www.peachparts.com/shopforum/diesel-discussion/194141-breaking-into-123-trunk-w-o-breaking-anything.html