It took me about 30 minutes to get the key to turn. The rubber pad on my sander was hard to hold in place at 12000rpms. Be patient and just keep pressure on the key. Get someone to help keep a little pressure while turning. Good luck

# days drilling lock is harden metal,went thru bits.However once out drove with screwdriver for weeks until I found a book that showed me how to diassemble the mess.

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1999 w140, quit voting to old, and to old to fight, a god damned veteran, deutschland deutschland uber alles uber alles in der welt

went at it with a cordless drill again, no luck. did notice something floating around in there... it's just behind the face of the lock but before the pins. it's not brass so it's not a pin... its silver and from one side looks like the edge of a penny protruding from a flat rectangle... i can move it around and the other side looks like a semicircle. Anyone know what this is?

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1984 300CD

Keep trying with the key instead of drilling or cutting, you may eventually get it to turn. It's the wafers in the tumbler sticking due to dirt and grime. Jiggle the key back and forth and use WD-40 to rinse out the dirt. In my 240D, took me 30 minutes of that and it turned finally.

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85 300D turbo pristine w 157k when purchased 167,870 July 2025
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

Go to a specialty fastener shop (nuts and bolts) and buy one of the bits pictured here.

I recommend one that a little larger in diameter than this. Somewhere in the 1/2" category. Its gonna cost you about $30+ but unless your wife's diamond is stuck in the ignition you won't have any trouble drilling it out.

After you get through the hardened face of the ignition use a standard bit and work it around to remove the tumblers. At some point you can insert a long small slotted screwdriver and turn the ignition.

Don't bother going to ACE, Home Depot or Lowe, Sears or other places. They didn't have them three years ago.

Good luck.

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These ign switches suck so bad. When you get done drilling or vibrating the thing apart, don't put the working key lock or lock pin back in . I took the lock part apart but left the cylinder to accept the key. 3 times my 190d broke its switch, it has a link between the locking portion of the assembly and the electrical switch in the back. Its' a 3/8 long pot metal tube with ears that shears off. Easily. oh, I remember some thing about the dash comes out for access. Position 2 in key rotation allows a stiff wire(2?) to be poked into it and push a snapring or such out and allow the lock cylinder to be pulled out. out The electrical part on the back has screws I think. Modify the switch asembly to look like the key is needed but not actually.And keep your mouth shut about it. She won't know, and she needs the key to lock it.it is not safe to replace the pin lock or the key lock because of the failure rate. It ain't safe for someone to be marooned over this, so.
To keep my 84 190 in service I did these things, after the 3rd fail. My 126 has a sticky switch lock and it's getting the same switcectomy when I break it out this spring.
I really do like my mercedes,very pleasant to drive. good luck.

anyone know what that bit is called so i can ask for one? also, i read to use electrical contact cleaner because it evaporates and dirt won't stick to it. any specific reason to use wd40?

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1984 300CD

At this point, it seems easier to me to pull the whole ignition assembly out and replace it.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

Souber Mercedes Ignition Lock Cutter.

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'84 300SD sold
124.128

It's a burr bit. If you have a Fastenal in your area they should have one of those.

Ugh!

Drilled out the tumbler with a 1/2" bit after chopping up the lock face with a dremel+cutting wheel. This was surprisingly painless.

Didn't escape this one without losing sleep though.

Tried drilling through the tumbler slowly and checking after each bit if the thing would turn over. Without warning, the drill spun spun the tumbler and turned the ignition, starting the car but we later found also snapped something in the ignition assembly.

After the lock turned, we couldn't get the dog to disengage and allow the black ring to spin off in order to remove the shell of the tumbler

To get at the dog, we drilled sideways up into it, when the chuck of the drill accidentally brushed the dash and the texture ripped a big chunk right off. I didnt realize how fragile the dash was, pretty upsetting after doing everything carefully as to not damage the perfect dash.

Getting the dog to drop was a ridiculous nightmare, toughest part of the job. Eventually we put a notch in the black ring with the cutting wheel, and whacked it with a screwdriver to bump it over the dog until it unthreaded.

After we got the ring off, we were able to pry out the end of the tumbler and figure out that we had broken the ignition.

Then we got to drop the steering column and remove the whole ignition assembly anyhow.

So, thanks to that little pin my car is a total mess, the dash looks like junk, and my ignition is shot anyhow.

Good news is that the ignition is pretty simple. The two halves unscrew from the back, behind the plug. A rod runs through the whole thing, from the ignition lock that makes contact with the tumbler, through a green plastic disc that actuates the shut off valve, and to the switch in the back. This rod snapped at the green disc. I'm repairing it by disabling the column lock, removing the ignition lock, and putting a new rod from the switch, right though the disc and out the front of the ignition to which I can attach a knob.

Hopefully this works and I'm able to patch the dash and cover up this hack job.

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1984 300CD

Wow sorry to hear you had to resort to butchering! I have a 1983 240D parts car if you need ignition lock parts.

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85 300D turbo pristine w 157k when purchased 167,870 July 2025
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

In retrospect, do you think it would have been better to remove the whole ignition assembly? Other people in similar positions may benefit from your judgment.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

Glad to see you got everything worked out! I may have to do something similar (hopefully not) and would like to ask the folks with experience here how this would relate to the gearbox not "seating" into positions. I also can not get my key out, however my car starts just fine. I was glad to see this thread and how you were able to correct the problem, agreed that this is a major PITA!!

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W210 1996 E300 - Daily
W126 1981 300SD - Nice weather
W111 1966 230S - Weddingmobile
AVPCAR 1999 Honda Si - Drag/Showcar
W111 1968 230S - Parts car

On my '82 300D I pulled the cylinder and then removed all the pins. This made it look like a regular cylinder, but any key/ screwdriver would work to start the car.

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$60 OM617 Blank Exhaust Flanges
$110 OM606 Blank Exhaust Flanges
No merc at the moment