I started a thread some time ago, asking for some advice on how to disassemble the tumbler from the chrome button on my 560 SL, which was missing the stainless cap and 'door' on the end http://www.peachparts.com/shopforum/tech-help/211492-any-lock-tumbler-knowledgeable-guys-here.html?posted=1#post1753949

As it happened, I got the advice I needed and logged in after I had already completed the job. Sigh.

Anyway, here's a how-to for anyone with a similar problem, or need to remove the lock tumbler from the button:

1. The button assembly is accessed from inside the trunk, visible after removing the latch assembly (3 screws) and the carpeting. Remove the screw attaching the plastic end piece to the vacuum pull rod, then the 2 8mm bolts holding the button housing to the trunk trim piece. Be very careful not to drop any of these into the recess at the back of the trunk.

2. On the workbench, use circlip pliers to spread the clip holding the black plastic piece to the lock tumbler. Then, using a sharp tool like a dental pick, work around and remove the large clip holding the lock tumbler barrel spring retainer in the casing (spring and clip just visible in pic 1 on the left).

3. Now for the trick part, removing the tumbler from the chrome button housing (shown in pic 1). Insert the key fully, and turn it (right, I think) a bit while pushing on the end of the tumbler and pulling with the key. You will feel it start to move out. After it is out about 1/8" or so, the pictured little ball bearing will fly out of the hole in the button casing, from the pressure of the little spring (pic 1, just below the button barrel).
Mine went somewhere, so I used the one from the donor tumbler I had. If you are aware of this, you'll put your finger over the hole while pulling the tumbler out!

4. I removed the stainless cap with the keyslot, the little flap 'door' that covers the slot when not in use, and the rod with the 2 little springs that keep the flap door tight against the inside of the cap, from my donor tumbler/button (from a W126 380SE trunk incidentally, which also shares the door handle with the 560SL).
The procedure to insert these pieces is quite tricky, took me about 6 tries and 3/4 hour, including time to locate flying pieces. The spring and rod go in first, then you have to position the flap door in its recesses under the spring's pressure, and then the cap to hold it all in place. I used a steel rule to hold the flap in, then a screwdriver through the cap slot, exchanging pressure from the rule to the screwdriver as I slid the rule out and the cap into place.

5. The donor cap was held on to the tumbler with 2 tabs. I suspect the cap on my SL tumbler was peened into place around the edge, judging by the 4 tiny indentations around the rim. So, I cut the tabs off and ground the edge down a bit to nearly match the tumbler rim depth, then with the whole affair in the vice, peened 4 new dents to secure the new cap in place. Pic 4 is blurry, but you can just make out the indentations.

6. I should mention that I left the key in for most of the work. When it needed to be out, I taped over the tumbler to keep the pins in place. The tumbler goes back in by inserting the key, aligning the 2 holes, inserting the spring and ballbearing, then push the ball in the hole while pushing/turning the tumbler into the button barrel.

7. Installation is the reverse of removal, of course. The end result was worth all the effort, as I can continue to use the same key as the doors and ignition, and no longer have an unsightly 'capless' button (which looked just like pic 2 sans flap piece). Now if I could just locate a nicer, not-so-pitted trim strip.....for a reasonable price....

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__________________
1986 560SL
2002 Toyota Camry
1993 Lexus

Hey Don,

I've got one of those trunks that doesn't open with the key when it's locked. I've taken it apart and I know what the problem is, but I can't see how to fix it.

The plastic ring that turns and is supposed to push the trunk latch doesn't go behind the latch when I turn the key. Instead it isn't far enough in to get behind and it goes just to the side of the latch. Can the lock cylinder be installed so it's not fully seated? If either the latch was 2mm further out, or if the lock cylinder was 2mm further in, everything would work the way it's supposed to. I tried washers under the truck latch, but that didn't work. If removing and reinstalling the lock cylinder would work I'd give that a try, but I don't know if it's even possible.

Hey Scott, only too glad to assist, if I can. I'm not so sure that the trunk latch on your SL works the same as mine though, from the problem described.
Pic01 is the position of the black plastic 'push' piece, trunk locked, either from turning the trunk key to the right, or from the attached arm pulling from the vacuum canister, as when the driver door is locked. The 'lock' position moves the black 'pushing pad' to the right (from in the trunk view) so it can't contact the latching arm when the button is depressed.
Pic02 is the unlocked position. The black push piece has moved into the center of the assembly, and is now positioned directly in front of the bottom part of the latch pivoting arm, shown in pic03. The key is turned left, or the attached arm has pushed it toward the passenger side.
In my setup, I can't visualize the same issue as you describe, but that could be me interpreting wrong. I had a devil of a time with meltedpanda's seat belt problem, internet tech is a tough communications medium....
Since the button moving inward is the 'force' that pushes on the latch arm, and this will only work if the black push piece is turned as far as shown in pic 02, I will assume you can't get the key to turn it all the way? Am I correct so far?

Edit: I don't think the tumbler can be inserted into the button housing in more than one way, so when it's in, the end, where the key inserts, is flush with the button housing and the key slot is vertical. The black plastic piece could be in the wrong position on the stub end, where the circlip holds it on (see pics), or the post/piece could be worn so it doesn't rotate properly.

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__________________
1986 560SL
2002 Toyota Camry
1993 Lexus

any way to get in if trunk is locked, and won't open with the key? can you remove tumbler if can't open trunk?

Just to add to point 3 the "trick" part, the trick with my lock, that was full of 30 years of dry grease and gunk, was to bash the end that holds the c-clip (i.e. not the key flap end) with a bloody big hammer.

also add, be careful on reassembly, since the chrome barrel can be installed in the alloy housing both ways, and held in place with the c-clip, then you go to install this in the car and wonder why it doesn't fit!!

refer to a picture, e.g. http://www.peachparts.com/shopforum/sl-forum/249924-trunk-lock-2.html for how it should all look when re-assembled.

also found that the key "leaves" for the laser cut keys (i.e. the ones with an 'L' shaped hole, as opposed to the rectangular hole for the double-edged regular keys) are cut in different ways between the door locks and the trunk lock, so you can't interchange these.

when re-keying it's easier to just to file down the 'L' part or dremmel down the protruding top surface depending on whether you need to go down a leaf number or up a number respectively (#5 has the tallest 'L' part, #1 the smallest).