My 300SDL vacuum door locks work fine. If I pull up either of the front door, uhh buttons, knobs (what do you call those things?) all of the doors and trunk will unlock. I have am an aftermarket remote opener, vacuum capable attached, works great.

My BMW E30s also had connected locking, used electric servos. I could lock the trunk on those with my key, would lock all five locks, gas cap lid also, but the trunk would not open if one of the knobs/plungers was opened on the front two doors or if I opened with the aftermarket remote. Gives extra security if your windows are broken or doors opened with coat hanger.

My 300SDL will not do that, it will turn 90 degress counterclockwise to open the trunk (and all doors) but will only turn may 30 degrees clockwise with no locking action. Search results had it as clockwise would unlock. The vid shows it what I have.

https://youtu.be/TkQn6L2KduM

So, what I'm wondering, if I took the lock out perhaps me or a locksmith could find the damage. Or maybe a boneyard unit with my tumblers installed or maybe a new unit - about $135. Anybody know?

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1986 300SDL, 362K
1984 300D, 138K

Probably a switch fault or a sticky lock cylinder. Locking the trunk should lock the rest of the doors (and arm the alarm). You may have a broken wire in the wiring loom, a defective switch, or something out of adjustment or in need of exercise in the lock mechanism. If you turn right 90˚ and pull the key out, it should set the deadbolt in the trunk lock.

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Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Turns to the right for full locking sounds like what it should do. That only makes sense, I appreciate the confirmation.

Complete wild ass miracle, today I found the first SDL ever at a Pick and Pull. Like mine, it’s white, different shade, but at least I wouldn’t have to paint the edges of the rear passenger door I want to get.

The rear lock looks intact, can’t test it without a key of course, I tried to take it out. There’s some rocket science involved I’m not getting. I didn’t have Allen wrenches with me, on the underside of the exterior housing, under the lock cylinder is what looks to be an Allen wrench opening.

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1986 300SDL, 362K
1984 300D, 138K

One lousy aspect of that rear door, not a mark on it, but it won’t open, even from the inside, the threaded rod to unlock it is not sticking above the sheet-metal like on all the other doors. The worst part is it’s about a half inch open, that is the trailing edge sheet-metal is about a half inch out from where it should be, and when you push in on it, it’s highly sprung. My best guess is it got tweaked on the hinges somehow.

I can maybe undo the bolts, two up and down, and get the door off the hinges and pull it out that way. Would be a lot nicer if it opened and closed perfectly of course.

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1986 300SDL, 362K
1984 300D, 138K

I have seen many SDLs in pick-n-pull near you, row 52 has been way out of date lately but last I looked there were 3 (not white ones) in the area too.

Update. I've decided that putting in new tumblers is a good thing to try. Could very well be it. It won't turn either way now. The assembly looks a lot like that on my W123 and it came out just fine.

Funny thing I can find no help on buying a cartridge. Perhaps it's just like the ignition tumblers, would be nice to find some affirmation of that. I've tried most of the usual suspects, no luck.

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1986 300SDL, 362K
1984 300D, 138K

Not long after I saw the one above I saw 2 at the Newark yard, both pale yellow. A couple of months ago I spied a really badly rearended 350SD. Had 280 on the odo but pretty clear it was runnng the day it was totaled. The engine compartment untouched. I pulled the FI pump out for my buddy, he gave me some funds for the work. Then I discovered it had a 14 head. We concluded that someone had replaced a bent rod 350 at some point with a 3.0 He checked it with his two 350SDs, they all had identical badging on the pump. I almost wish I'd had the time and money to take the whole engine out. OTOH, no telling how high the miles were.

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1986 300SDL, 362K
1984 300D, 138K

Now I might be getting somewhere. Apologies to Pelican, this is from a competitors page, but Pelican doesn't carry this. Doesn't appear that ignition tumblers could just be dropped in. But then you can sort of tell that by examing it. Turns out this part is for models just after the SDL, doesn't fit, but it is useful to look at.

At this point I'm going to remove what I can of the tumblers and see if they are somehow serviceable.

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1986 300SDL, 362K
1984 300D, 138K

on my 560SEC the key must be removed in the 9-3 position
for the central locking to work the unlock

if the key is removed in the 12-6 position all the way right
the central locking will not open the trunk lock.

Don't want the valet driver snooping around in your trunk

That's the way it is in my W123 300D.

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1986 300SDL, 362K
1984 300D, 138K

OMG, I love/hate autos. The tumbler body on my W123 looks similar, it came out easy enough. I can't get a metric Allen wrench to insert here. Went from really small to too large. I tried a small philips, two of them, no luck. I haven't tried a flat screwdriver yet. Tomorrow I try to start an allen wrench on the W123.

Anybody know?

It's the sort of thing that would be great to have on file somewhere. Dream on.

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1986 300SDL, 362K
1984 300D, 138K

If anybody read the above, please allow me to apologize for the dumbassery. No way is MB going to have an Allen screw accessible to the world that disassembles the rear trunk lock. I do recall it being a lot easier on the W123. I suspect that hole is for drainage. OMG I would dearly love to get this trunk lock working in optimal fashion.

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1986 300SDL, 362K
1984 300D, 138K