Thanks to many other forum posts I was well aware that the ignition cylinder in my 1984 300td someday might refuse to turn. Without any advance warning it finally happened. One day everything worked fine and the next day the dreaded 'my key won't turn.'

Miraculously, within twenty minutes of turning, shaking, lubing, and vibrating I got it to turn long enough to re-position my car first in line in the driveway and shut it off.

Yes, I violated the #1 rule-if you do get the key to turn by all means DO NOT turn it off.

Before pulling out the key i tried to turn it back and forth a few times and everything felt smooth. Made sure the wheels were straight with no tension on the steering lock, checked the key by turning it one last time (it was fine) and then confidently removed the key mentally prepared to repair it the following day.

The next day dawned, I made my way to the car, inserted the key and it would not turn. For the next several hours and well into the following day I tried everything (+ every variation thereof) I had ever read on this forum and others without success.

A quick list of the methods: new factory key with and without pliers, vibrated the key and cylinder with a hand-held massager and sander (massager seemed more effective), jacked up the front wheels and had a helper try to turn them as i tried the key, all kind of liquid including WD40, PB Blaster, Kroil, Brake Kleen, tried every possible combination of turning, jiggling, pulling/pushing the key in/out ever so slightly while turning.

So I resorted to the method of removing the entire lock assembly from the steering column by grinding off the tip off the pin that holds the assembly in the column and forcibly pulling the column to get the lock assembly free of the dashboard and out of the column. It involves pulling the cluster, loosening and moving a pinch clamp on the lock assembly to reveal the pin. I think Diesel Giant has a how-to with photos.

With the column pulled down and the lock assembly free of the dash I discovered why my key would not turn. When the ignition key is inserted the end of the key pushes a small chisel-shaped metal tab which allows the steering lock to retract from the column as the key is turned. Unless the tab is depressed the steering lock can't retract and the key won't turn.

But with the entire lock assembly in my hand I could push the steering lock into a retracted position and the key would turn. I spent about 15 minutes studying the way everything worked and was amazed how little the little tab needs to move in order to permit everything to work. On the flip side, if it doesn't move that little bit nothing else is going to turn.

One thing I noticed was if the steering lock was pushed in too far there was no noticeable click at each key position. The key just kinda flopped back and forth. So I decided to "fix" things by pinning the steering lock back in the shaft so that it could not engage but not so far back that I would lose the tactile sensation of each key position.

Figuring the steering lock would be hardened I wanted to avoid having to drill through it. Luckily, with the steering lock pushed into the optimal position, there was about an eighth of an inch (little over 3mm) open at the end of the shaft I could drill out without hitting the hardened lock.

The shaft drilled pretty easily and I used a small nail as the pin. Cut off the protruding ends, peened them, and filed everything smooth. The peening bent the nail slightly so it couldn't easily come out.

While everything was out and apart i degreased the ignition lock cylinder with lots of Brake Kleen so I could begin to again use graphite as the lube.

The reassembly went pretty smooth except it did seem harder for everything to clear the dashboard than it did taking it out. Be sure to connect the electrical plug to the back of the ignition BEFORE pushing everything in place. There may be a way to fiddle the connector in place afterward but I sure didn't see how. Be aware that key position is critical to disconnecting/connecting the plug. In 1984 (perhaps other years) there is a white plastic T that turns with the key and must be lined up with a slot in the plug to plug/unplug it. IIRC it is key position zero.

Also as the how-to describes, be sure to note which of the two vacuum lines is which on the ignition shutoff before removing them (tip- on my 84 one has a blue stripe). On the reassembly you can push the vacuum lines on after getting the ignition lock/steering column in place if you leave the rubber connectors attached to the shutoff valve. Just reach through the cluster opening.

The biggest surprise I encounter is the damage that can be done to a portion of the steering column when pulling it down to free the steering/cylinder lock assembly.

At some point in the W123 series Mercedes began to use a hollow corrugated tube in the steering column. The tube protects the driver from being speared in the case of a severe frontal collision. The piece runs from the firewall and attaches to the rigid portion of the steering column about 20" down stream of the steering wheel.

When pulling the steering column down to release the steering/ignition lock assembly that collapsible corrugated tube can get bent. Nowhere in any forum instructions did I read anything that gave me a heads-up on this potential damage. In looking at it (and diagrams of the column assembly) before pulling the column down it appeared to have a ujoint so I never considered the possibility of a problem. It was only as I reassembled everything that I noticed the tube had bent and a small rubber disk attaching it to the rigid portion had cracked. So be forewarned!!

One unintended consequence of pinning the steering lock is now my car thinks I've left the key in and buzzes even after it's pulled out. To prevent the buzzing simply disconnect the single wire from the bottom of the ignition switch but sure to remember to remove your key.

To summarize:
1) if your ignition key won't turn and you somehow do manage to get it to turn, DO NOT TURN IT BACK PAST THE NUMBER ONE POSITION!!! This may your last chance to fairly easily diagnose and repair this problem without having to stand on your head to accomplish it. if your car is running reach under the hood and manually stop the engine then carefully remove the negative cable from your battery.

2) just because your key won't turn doesn't automatically mean your ignition lock cylinder is bad. It could be the cylinder, it could be the steering lock, it could be both. if your key won't turn consider trying what I did instead of calling a locksmith and/or drilling out the lock cylinder.

For the ideal fix I would have spent $175 or so on a new steering lock assembly and another $100+ on a new factory lock cylinder. But this repair got me back up and running.

Thanks to everyone in these forums who has posted their tip(s) on this problem. Without their advice I couldn't have pulled this off!

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Since I currently suffer from the same malady, it might be of interest to yourself and others to understand that you are perfectly fine with turning the key back to the original locked position.

SIMPLY TURN THE STEERING WHEEL 90 DEGREES FROM CENTER.

Nothing will lock and no problems will be encountered with the lock mechanism as it never engages the steering column.

This situation is one where the ignition cylinder has previously been replaced (within the last 50K miles) and the suspect is the lock mechanism to the column. Therefore, I cannot be certain if this approach will work if the lock cylinder itself is worn.

Thanks, Brian Carlton, for adding to my comments. You are a longtime contributor to this forum and may very well know more about this than I do. The point I wanted to convey to others is do what is necessary to keep your key turning particularly if you are planning to repair/replace any part of the ignition/steering lock assembly.

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Is this the Chisel shaped part you were speaking of.

If so when you insert the Key the tapered end of the Key pushes in on it.

Attached Thumbnails

 

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84 300D, 82 Volvo 244Gl Diesel

If yours broke like mine, I am guessing the problem is behind the part that Diesel911 shows. There is a spring-loaded detent behind there. The spring housing is weak pot metal and easy to break (just a question of time). Once it breaks, the parts jam the switch from turning.

To get to it, I had to remove the key arm from the column (look for release pin on front), then pick open the swages on the aluminum housing that hold a steel cover plate to remove that plate. I just left the broken parts out, so don't have the detents anymore (sounds like you don't feel them either), but the key has never self-rotated that I know of (my son drives that car, poor communicator). I recall that I used epoxy and swaged the aluminum (hammer & chisel) to re-secure the plate. I was tempted to leave the steering lock rod out since I doubt that helps much with security and adds some driving risk, but decided to leave it.

I have posted this several times, but it doesn't seem to "take" and people keep fooling with their lock tumblers to no avail.

25 yr old diesel Mercedes aren't on the top of car thieves lists. I think removing the steering locking pin is a good idea when the lock is apart. On my daughters 84 SD, the locking bolt broke loose from the locking assembly, dropping into the hole in the column and stopping the wheel from turning. Luckily this was at a very low speed. It wouldn't be nice if this happened at high speed on a winding road.

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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

On mine I pused the Locking Bolt/Rod in and pused that button that you have to drill out when the Key is stuck In (that holds the Bolt in place) and epoxied the Button down.
I now have no Steering Wheel lock.

I for some reason I want to restore it I need to scrape out the Epoxey so the Button functions normally.

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84 300D, 82 Volvo 244Gl Diesel

My current situation with the SD seems to indicate the the locking pin is not going to solve the problem of the inability to rotate the ignition tumbler.

The mechanism between the tumbler and the pin appears to be the culprit, and, the pin itself whether present or not, won't cure the issue. Please advise if not correct.

There are several posts regarding curing the mechanism problem. Some suggest that it can be done without losing the detents...........others not.

I have to approach this at some point, relatively soon, before I forger to turn the wheel 90 degrees.

Hi Bill,

Since I'm forced to address this issue on the SD and don't have a clear direction with regard to the mechanism, can you comment on this thread whereby he doesn't remove any of the components in the mechanism:

http://www.peachparts.com/shopforum/diesel-discussion/283114-steering-lock-repair.html


EDITED: The time and effort to chase the issue with a 30 year old assembly isn't worth it to me when a new OE lock can be procured for $153.

Sorry, I don't know. In my situation, once the locking bolt separated the key would turn and start the engine but wouldn't pull the bolt out of the steering column.

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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

Got it. That makes sense if you have a complete mechanism failure and the bolt is no longer connected to the mechanism.

I'm going to take a different approach. Since I need to remove the ignition lock anyway, a brand new OE lock can be procured for $153 complete with electrical switch and vacuum connection.

Why screw around with the existing one........it's hours of assembly and disassembly and the old electrical switch is still present.

For a W123:
I received the new Steering Colum/Ignition Lock Housing from Mercedes (1264620730 $144 free shipping) and on the Box it has Made in France. (It came without the Seat Belt Buzzer Switch but has the Vacuum Shutoff Switch and the Ignition Switch.)
Cast into the Housing is Neiman.
One of the Internet Sellers advertises the OEM Steering Colum/Ignition Lock Housing as made by Valeo/Neiman. So Apparently that is true. If I had bought a Valeo Housing I might have saved a little.

The Valeo on sells for less.

The Itnition Switch that came with the Mercedes one had Made in West Germany on it and it lacked the rotating Plastic Key that locks the Electrical Connector to the Ignition Switch unless the Key is in the Proper position.
This means even without a Key the Electrical Connector and the Ignition Switch can be removed.

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84 300D, 82 Volvo 244Gl Diesel

Thanks for the info.

Any issues with the install (special tricks?) and did the ignition key cylinder fit without any problems?

I'd like to find a procedure to follow without reinventing the wheel. Be nice to do it in a couple of hours.

If it's the same as my problem was, simply do not remove the key from the ignition. The steering wheel is not locked until you remove the key from the ignition. If you pull the ignition switch, you can prevent the lock from ever engaging, by deforming it so that it doesn't move all the way out. Your steering column will not lock until the ignition switch is replaced. I would imagine with the steering wheel lock in the unlocked position (tab is inside the cyilnder) a little bit of strong epoxy will keep it there. This should not effect the operation of the ignition, other than allowing the key to turn all the time. Now granted there might be some situations where the steering lock isn't the cause of the key not turning, could be the tumblers, or a bad key.

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Closing the store
Benzbonz.biz on your smart phone or tablet.

I think what ever tricks there is are already in the DIYs.

Since I was able to turn the Key into the proper position I got the Tumbler Out.
That also allowed me to pry off the Electircal Connector from the Ignition Switch.
I was able to get the Colum Lock out without lowering the Steering Colum but it was a sgruggle.
The new Colum lock is at least 1/4 inch shorter and that made it only a tiny bit easier to get it back in place without lowering the Steering Colum.

I had trouble removing the Safety Belt Buzzer Switch from the old Lock so I cut the one of the lips on the Colum that holds it in.

Boths sides of that Seat Belt Switch have a Plastic sort of hooks that need to be depressed to remove it. I did not try this but a Bobby Pin through each side may be able to depress the Hooks.

Also the Steering Wheel Lock Plunger needs to be in a position that depresses the Safety Belt Buzzer so you can shove it out without breaking it off.

I threw My old Tumbler into a Sonic Cleaning tank with Water and Purple Power and cleaned it until no more stuff came out of it. I reused the Tumbler and have had no issues so far.

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84 300D, 82 Volvo 244Gl Diesel