So I thought about Michael's idea and it sounded better and better the more I thought about it. All I needed was some 1/4" keystock in brass. I looked around and I couldn't find any locally at the big box places. All the little hardware stores have gone out of business in my area. So I started nosing around in my garage and I found these old door knobs we took off years ago. They have a 1/4" mild steel square stock that goes from one knob to the other through the door.

I put one in the vise and went to work. I felt too lazy to set up the mill so I figured, hey, how long would it take with a file and hand drill? Doesn't need to be pretty. Answer, I did this in 50 minutes. I'm no artist but I think it looks okay for my simple tools. I used a medium sized mill file, a hacksaw and a Milwaukee battery powered drill. I drilled it a bit ugly but it isn't critical. I think it'll work.

The bar stock from the door knob.
https://live.staticflickr.com/65535/...9b4803eb8c.jpg

First cuts to get the tombstone shape.
https://live.staticflickr.com/65535/...fbc0c1dafc.jpg

Filing the face and the side cuts.
https://live.staticflickr.com/65535/...fd19dd069d.jpg

Done. Mine on the left. Original on the right.
https://live.staticflickr.com/65535/...41be610978.jpg

The hole could have come out better on the mill. But I decided to use the M18 hand drill. I figured nobody will see this. But I know it's in there. :(. Someday the new owner will take it apart and swear at me.
https://live.staticflickr.com/65535/...c3e59dbc1c.jpg

There it is. A little sloppy. The original was .272" square. The door knob stock was 1/4".

https://live.staticflickr.com/65535/...c45ff5a8b3.jpg

Used simple tools. No fancy small files. Most of the work was done on mill file and some of the details were done with the hacksaw - which is kind of a narrow kerf file. I burned a few calories but really it was less than an hour. Cutting a little at a time and checking helped keep things from getting away from me. Now I have to take the steering lock out again to try it. I shouldn't have put it back in but I really wanted to drive the car yesterday. Oh well. Maybe later.

I bet if I did it again it would come out better.

https://live.staticflickr.com/65535/...e697cdcc68.jpg

Failed at lock restoration.

So I really didn't like my hand filed latch. It was too sloppy in the hole and wiggled around too much. I didn't feel like tearing the lock out of the car again just to find out it was out of tolerance and I'd need a better fitting latch.

So I got the crazy idea to braze on some brass in the wear grooves on the original latch. Then the plan would be to file the brass down and I'd have a restored latch. Well I failed big time.

The latch was not red bronze like I had thought. It was pot metal. Pot metal plated in copper then chrome on top of that. So it looked bronze under the chrome. But it was some kind of die cast zinc aluminum alloy. Three seconds under the brazing torch and it turned to slag.

https://live.staticflickr.com/65535/...6468e74d49.jpg

Looks like I'm going back to the drawing board. Bottom line, do not try to braze that little latch.

Ok, the latest. I found a True Value hardware store nearby that had 5/16" square barstock in steel. Brass would have been easier to cut. But I figured I'd take the extra time and file out a steel pawl. It isn't perfect. Obviously hacked by me with files and a hacksaw. I roughed it out on a grinder first then I did the detail work with a mill file. It fits much better than the one made with 1/4" square stock.

Amazing what you can do with a file and some patience. Cut, check, cut, check, scribe, magic mark for dykem. I spent two hours working on this. Most of the time was drilling the hole. It came out a lot better than the first time.

At some point I'll take the lock out of the car again and try the part. I think it'll work but I've been wrong before. This thing has to be really reliable or it has the potential to leave me stuck someplace with a jammed ignition lock.

I'll update when I have it in and tested.

Sadly the original was pot metal. I'm sure I could fill it in with some pot metal repair solder but it would be soft without the chrome plating. I like the idea of steel.

The shape is just a bit complex for 3 axis cnc. It can be contoured but it will still take a couple of setups. The drill hole is a pain too. The more I thought about it, if I wanted to do this again I'd look into investment casting it in bronze. I can probably make a positive on my 3D printer and do kind of a lost wax process. But that is all theoretical. Haven't tried and I don't think I want to mess with this anymore.

Honestly the best solution is taking out the lock and gutting the steering lock bolt and cam. There is a risk that somebody in the know can easily steal the car. My recollection is the car can be jumped under the hood with a pair of pliers across the screw terminals on the fender. And I think if you unhook the vacuum line to the fuel pump you'll turn on the fuel...soooo, yeah, probably my car is incredibly easy to steal if the miscreant is informed about Mercedes diesels and happens to know mine doesn't have a column lock.

Anyhow here are the latest images. This is crazy. I don't think I'll have to deal with this again. Unless I get some crazy idea in my head and buy another MB diesel.

The final (left) edition with the stub of True Value keystock.

https://live.staticflickr.com/65535/...31384a9efd.jpg

Will be interesting to see if it works this time.
https://live.staticflickr.com/65535/...580a6fa134.jpg

Not pretty but I think it'll be functional.

I decided to take a third crack at this problem. I really wasn't happy with the fit of my second attempt at this part so I cut it again.

Here is the second revision. It is a still a loose fit. Better than the first but I wasn't happy with it. I figured I had most of the barstock left. Why not? It'll be better with each attempt.

Here is the second rev. It's sloppy. Lopsided. The spring hole isn't centered. There are a bunch of issues.

https://live.staticflickr.com/65535/...b6d3c8613f.jpg

Here is Revision 3.

https://live.staticflickr.com/65535/...9ccbd4709b.jpg

I decided to stop avoiding my milling machine. I don't like cleaning up all the steel chips mixed with cutting oil it makes so I don't turn it on. I hate steel splinters too. Silly. I milled the 5/16" bar to the proper outer dimensions. Then I drilled the end in the vise with a tiny carbide drill bit to set a perfectly centered pilot hole.

From there I put the part in the vise and shaped the angled face and the tombstone shape by hand with a file. It was a lot easier now that the sides were parallel.

Again I improved my technique of magic marker, file, measure. It's amazing how you can remove a mil at a time. It just takes patience. I'm not sure if I should be proud of this "skill" but I have improved at making things with a file. The learning curve is addictive.

Here is a comparison of the parts. Original, second rev, third rev.

https://live.staticflickr.com/65535/...627893a400.jpg

https://live.staticflickr.com/65535/...efc1f12c2d.jpg


Hole is centered better too.
https://live.staticflickr.com/65535/...fb747580d7.jpg

Okay, maybe tomorrow I'll reinstall it in the lock and test it out.

Finished!
 

I assembled the lock today and got it back in the car. It works. But there are some important end notes to this project.

When I put it back together it still jammed up. I tinkered with it hours trying to get it to work and I just had no luck. With the cylinder out it worked with pliers turning the steering lock manually, but when I put the cylinder in and used the key it wouldn’t turn. It would bind up immediately. The steering lock wasn’t even letting me turn the key 10 degrees. It was worse than when I had the original part in the lock.

So I started to really look hard at the innards of the steering lock mechanism to see just how it worked and why it was hanging up. Getting to the bottom of it would probably be good info because whatever was causing my lock to jam is causing havoc on owners all over.

This is a very German mechanism and it has a lot going on inside. I cannot put into words how this thing works. There is too dang much going on and I cannot clearly explain it.

In short the little pawl I made is the cause. It’s made of pot metal and it deforms. Turns out the design is very sensitive to the dimensions. That ramp has to hop the key tip as you first rotate the lock. On my first prototypes it did not.

The sloped face needs to be smooth and the right length. I fine tuned the length on my last prototype till I got the lock to work smoothly.

So it basically boils down to the dimensions of this part. Specifically the dimensions of the tip.

https://live.staticflickr.com/65535/...13f5ae420d.jpg

I think what happens is it’s made of pot metal and it gets all deformed and gouged up. The shape of the face is important. It’s function is to hold the bolt back using the key tip. The idea is when the key is in the ignition the steering bolt is held back after the first time you turn it…yes it has “memory” and is technically a “latch”. It glides over the key tip and catches to hold it self in place. The engineers didn’t want you shutting down your engine and coasting only to find you also locked your steering. So the column won’t relock until you pull the key.

https://live.staticflickr.com/65535/...e4b225fc62.jpg

Once it deforms, the ramp doesn’t slide well on the key and it cannot hop over the tip into the latch up position thus jamming the lock. Also that ramped portion has to slide freely in this slot. It cannot if it gets all deformed and widened. This may cause binding. It needs to slide freely up and down in this slot. The deformation made it so wide it may have been biding.

https://live.staticflickr.com/65535/...626a98d556.jpg

I know I am not describing this clearly. It’s too dang complicated in there and there is a lot going on.

Bottom line is the problem is this little pawl part getting deformed on its stop. But if you are going to make your own from bar stock be ready to fine tune it’s dimensions to get the lock to function. Despite it being cheap pot metal it has a narrow tolerance to function.

Before making a new one I think it’s worth trying to try to cold forge the original into is old shape with a small hammer and try it out.

Im going for a drive now. :)

ETA - hey the light bulb just went off in my head. If this lock jams, and it is the steering column lock and not the cylinder, here is how you get the cylinder out without drilling. Go out and get a cheap copy of your key at a local locksmith. Bring it home and file off 2-3mm off the tip. Put it in the lock and open it as you normally would.

If the problem is that little ramp piece not being able to hop over the key tip, you just lower the bar per se and cut the tip off the key. The tip doesn’t hit any of the tumblers. It just locks up the little latch to keep your steering column bolt from activating.

Just a crazy idea. I was looking at this photo and I realized you just want to get the tip of the key out of the way so the ramp can slide past it without any interference. Of course your steering bolt will drop wen you shut off the car before you remove the key but who cares. The object is to get the cylinder turning so you can extract it without cutting.

Of course if something else has failed like the pot metal in the lock has cracked apart (which we’ve seen) then this won’t necessarily work. But it’s probably worth a try before you get the die grinder out.

https://live.staticflickr.com/65535/...a47fa69166.jpg

I've been following your progress and I'd like to thank you for both your perseverance and taking the time to document your efforts. I'd have probably given up and yanked the bits that lock the column.

Michael

Thanks for posting your detailed work. I fixed a jamming key switch in my 1984 300D ~10 years ago. Thought I posted, but can't find. My problem was deep inside, from broken parts in a spring holder. That gives the detent clicks as you turn the key. Must pry off the steel cover in 1st photo of post 6 to see. While "in there", I should have just removed the steering lock rod since it adds little value. Last thing I want is the steering wheel to lock while driving and better ways today to prevent theft. Without that spring, the key still stays in position while driving, so don't miss the detents. I found a photo of the broken parts. I crimped the steel cover back as best I could and added epoxy to help secure it.

Perhaps if you remove the steering lock rod, the worn ramp part you replaced isn't needed. A long time since in-there, so forgot how all the parts mesh. Like many M-B systems, perhaps over-designed.

Thanks. I hope this helps somebody. I think I’ll disassemble my steering bolts if there are any issues. I must say it was a lot smoother without all the guts. Hammering the little pawl back into shape is another good option. I think I took this one a little far. I really didn’t even understand how the thing functioned till the end.

I reassembled with my black plastic tumbler cover instead of the metal one. I will run this for an indefinite period till I feel good enough to put the metal one on. I still want the option to take this apart with simple tools if it jams again.

Food for thought. I think I’ll give this a try in the boy’s 300SD.

https://youtu.be/AhR9JS-Op6k

Michael

Ps, Impalaman just finished replacing a rear wheel bearing in the car he’s sitting in. Looks like quite the adventure.

Wow. Looks like he’s on to something there.

I dug up this image I took of my bolt pin. You can see it has a burr on two of the sides. Perhaps that catches. I feel kind of dumb that I didn’t file that down smooth before putting it back.

https://live.staticflickr.com/65535/...6247c1d295.jpg

It’s kind of odd though that both my locks still jammed up after they were out of the car. Maybe he’s helping the bolt along by twisting it to the right. He may be able to put a significant amount of pressure on the bolt tip by bending the wheel over to the right.

Anyhow that’s a good trick to get it moving. It may be able to save a drill job.


I still think the problem is on this little part.

https://live.staticflickr.com/65535/...626a98d556.jpg

The little ramp has to move side to side in the slot and plunge up and down into the slot at the same time. If it gets mushroomed out so that it’s wider than the slot & it cannot drop down into the slot. This causes the mechanism to seize. You can kind of see the gouges on the slot’s inner edges in the above image where the latch was interfering with the slot. In the image you can see the end of the latch has deformed to the point where it won’t plunge down into the slot.

Maybe his bending the column was helping the mechanism along. It’s almost like he’s pushing the bolt back out of the column with his direction of force. It is certainly a good trick and he’s doing something. I just don’t think his explanation holds water.

I wish I’d kept the bad steering lock on my 240D. I kept it around a long time hoping to fix it but I couldn’t figure out how to open it. Then I tossed it as junk. It would have been great to verify that hammering that little latch back into square would help. I’m really wishing I’d tried narrowing that latch width with a hammer and trying it before accidentally melting it.

I’ll have to wait till I wear one out to try experimenting again. That may be a long time since my new latch is made out of mild steel. My 85 300D is still stock, but it’s low mile and the lock is smooth.

These are incredibly hard to pull at the junkyard without the key.

Follow up. My internal catch for the steering lock bolt is working very well. I realized later that I forgot to polish up the lock bolt where it meets the steering column. My bolt was pretty gouged up after 40 years. It still needed the steering wheel wiggled to turn the key.

Recently I lost my ignition switch. The contact in it that handles my blower had gotten unreliable. No go for summer. I'd start the car and sometimes the blower wouldn't turn on. It would turn on when i turned the key then shut off during cranking as it should, but then it wouldn't start up again when the key recoiled to the run position. Anyway it is an old switch. Had to go. It meant I'd be in there again and I would get a chance to hone up the lock bolt.

I polished out the gouges with a file and then I broke off any sharp corners with the file. It helped a lot with the smoothness of the unlocking action.

I decided to try a new switch. Instead of buying OEM I decided to try my luck with a Chinese switch. (spoiler alert it was a dumb move.)

The switch was A-Premium brand from an online retailer. It was bargain priced at $17.99 with shipping included. I bit and I regretted it. The switch looks like satisfactory quality but there was a tolerancing issue inside the switch. If I tightened the three mounting screws on the switch the switch would bind up with a lot of friction. I tore the switch apart three times and tried different modifications with a file till I finally figured out the bad dimension. Shimming was required to get the interfering parts to clear one another. Clearly not a bargain.

Just thought of that when people here say cheap Chinese parts not a Mercedes makes. :P Certainly the case with the cheap switch. I know it was kind of a critical part but I reasoned I may not own the car much longer due to NLA parts issues so I decided to go cheap. I figured if it failed I could always jump the starter under the hood with a wire on the terminal block if I needed to get home.

Well my Chinese car is all back together now and the ignition is super smooth. i cleaned up the little contacts on my old switch with sandpaper. They were burned up. I'll save it in the junk pile.

Some images of the lock bolt resurface job and the A-Premium switch.

Gouged bolt. I totally missed cleaning this up last time. Before.

https://live.staticflickr.com/65535/...3be9f529e9.jpg

After.

https://live.staticflickr.com/65535/...680e270ff9.jpg

Trying to find out why my "A-Premium" switch bound up after assembly. Did some filing and shimming. When the three screws get torqued in the switch body the whole thing binds up. It needs a 0.015" shim between the plastic switch frame and pot metal body. Took an hour to figure this out. Disaster. Should have sprung for OEM.

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https://live.staticflickr.com/65535/...1040f9dc6b.jpg

Very nice! Hope your last repair means you don't have to revisit it for quite some time.

I'm probably going to regret not buying a new ignition switch wire harness housing. I finally went to reinstall the assembly in the column and I could not remove the wire harness from the assembly. Of course I had to superglue the switch back together since it sprung loose all the pins when I removed it. I managed to cram everything in the proper position without disconnecting things. I'm really hoping I don't have to be back inside of it for the switch/lock/tumbler/whatever else could go wrong!

If your switch fails you can still open it without unplugging it and pulling out of the car. The metal housing has these three spring tabs spaced at 120degrees around the side between the screws. You can see one of the slots on my photo above. You press the tabs in and the switch releases from the housing. There are two spring detents that fall out so put a big rag out to catch them. Once you expose the guts of the switch I just used a narrow strip of 500 sandpaper to clean up the half dozen contacts.

The ones that’ll be burnt will be those that carry the highest current. The blower circuit and the starter solenoid circuit.

Just saying no worries, it can be refurbed without unplugging.

Let this be a lesson; if the dealership can order both the lock and the ignition tumbler ORDER IT NOW. If you can afford it, order TWO (2), one as a back-up.

Good advice if you want to keep these cars in the indefinite future.

The tumblers for my SD are already NLA. They don’t even have a crummy Febi unit for my car.

The column lock is NLA and it is hard to recover from the JY because it’s locked in the car. Bring a cordless die grinder and a wire cutter. You cannot even unplug the harness on some switches without the key. That’s why I refurbed mine in this thread.

Writing is on the wall. Going forward I’m questioning every repair on my cars. Do I want them to last another forty years or is there a cutoff point where I just quit and buy another make?