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Steering Lock Repair

on the 1983 300CD-T (W123)

by dogguy


image 300CD: Yep, ignition tumbler turns no more

Here's how the ignition tumbler is supposed to function:
(Note- there is no sound on this video)
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Happily, I was able to eventually get the tumbler to turn to the second detent (the “ignition on” position) and ultimately remove it without going through the “can’t get the tumbler to turn” (horrifying) procedure.


1. I removed the key itself from the black plastic “fob”. This way, I would more easily and effectively deal with it during the procedure.

2. I acquired a hand orbital sander (item #40070) from Harbor Freight (around US $10.00).

3. I turned on the sander while touching the vibrating part to the key. I just worked it back and forth on the key for several 30-second periods. BE CAREFUL TO HOLD THE SANDER SO AS TO PREVENT IT FROM TOUCHING THE INSTRUMENT CLUSTER FACING AND/OR DASHBOARD AND DAMAGING IT/THEM.

4. Carefully, I used a pair of pliers to grip the key head and turn it left and right repeatedly in an effort to ultimately get it to turn to the second detent. This didn’t work the first few tries.

5. I repeated steps 3. and 4. multiple times.

6. I sprayed some Wurth HHS 2000 lubricant into the key hole. Several days earlier, I had done the same thing with WD-40 and let it sit overnight.

7. Eventually, using the pliers and carefully gripping the key head, I was able to get the tumbler to successfully (without forcing it) turn to the second detent.

8. The next step was to insert a straightened small paperclip into the slot on the side of the tumbler so as to force the pawl located on the side of the tumbler to retract. This is required so that the black metal ring on the outside of the tumbler can be unscrewed. Remember that you must keep pushing in the paperclip (that is, retracting the pawl) until the black metal ring is completely unscrewed. NOTE: The instructions stated to line-up the slot on the tumbler to the second detent and then insert the paperclip to force the pawl to retract. This was not helpful and didn’t work. I used a very bright light while carefully turning the tumbler until I could see down the side of the tumbler and discover the hole where the paperclip would go. It turned out that the tumbler had to be turned back a bit toward the first detent in order to find the pawl hole.

9. Next, the tumbler and black metal ring lift out of the car completely.


A. I’ve yet to find ignition tumbler replacement instructions in the factory manuals. Instead, I used the Haynes manual (moderately helpful) and the instructions (most helpful).

B. With the steering wheel locked, I had the vehicle towed on a flatbed to my garage. There was no way I could do this work without ready access to my tools, chemicals (lubricants), lighting, and 110v power. The tumbler locked-up while the vehicle was in a parking lot about eight miles from home.

C. Once I had the tumbler and black metal ring removed, I did a thorough cleaning of the insides of the ring and what it threads onto since both were well coated in lubricant from earlier work.

D. I had one heck of a time getting the large electrical connector located on the back of the ignition assembly to release. First, the clearance is awful there with the black plastic hose that connects to the left dash vent. I disconnected the hose at the console end and pulled it toward the driver’s door enough to provide clearance behind the electrical connector. Next, you may have to gently and carefully wiggle the key/tumbler a bit in order to get the connector to release. Whatever you do, don’t force it out the connector.
Once I have the replacement tumbler/key from Phil, I’ll be re-installing. From the looks of things, that work should be substantially easier.

Installation complete - some final notes

1. You *must* have the key/ignition tumbler in the second detent position in order to be able to successfully release the large black plastic electrical connector on the back of the ignition assembly. This is because the connector itself has a hole (shaped like this: |----| )in the center of it which is the receptacle for a pin that is the same shape. When the key/ignition tumbler is in the first detent position, the pin is in the hole and turned and thus is holding the connector in place so that it cannot be removed.

2. The new key/ignition tumbler’s pawl (the *whole* L-shaped thing on the side of the tumbler) must fully retract on installation and fit into its spot perfectly in order for the black metal ring to properly situate. If the ring’s detents don’t line-up fairly closely with the key positions as it did when the car was new or whatever, try the installation again because things are not right yet. In my experience, there will likely be an audible click (probably the pawl completely popping out of the side of the tumbler) when the tumbler and ring finally situate properly and as they should be. If you cannot turn the new key/tumbler with it and the ring installed, things aren’t right – try again. REMEMBER, to release the electrical connector on the rear, you must have the key/tumbler in the second detent position.
My tumbler lasted 245,000 miles/25 years and 9 months. Not bad. In fact, nothing short of remarkable. Just consider how many times that thing was turned. Whew

Update on ignition tumber, etc.

Unfortunately, a few days/drives after completing all of the re-installation activities for the new ignition tumbler, I found that the tumbler wouldn’t turn again (argh). Ultimately, the problem proved to be a failure of the mechanism inside the steering housing lock assembly. This is the gray metal L-shaped assembly (about as long as your outstretched hand) that the ignition tumbler fits into, secures to the steering column, and which locks the steering wheel. Once I had this part out of the vehicle, I could clearly demonstrate that it was the internals of this part that had failed and were causing the steering wheel to remain locked when it shouldn’t have been. This is not to say that the old (original) ignition tumbler was in fine shape. My summary of this project is this: Do not be fooled into thinking (as I was) that after more than 20 years of use, only the ignition tumbler wears. My experience has proven that the highly complicated steering housing lock assembly (and its operation is a fun project to analyze) wears just like most everything else on the vehicle. Now that the ignition tumbler and steering housing lock assembly are new/replaced, everything is tight and smooth – probably how it was in Dec. of 1982 when they built/assembled the vehicle. Good thing all of this lasts so long because this is quite an unpleasant job, ESPECIALLY when you cannot turn the ignition key anymore (my case). And this is coming from the same person who replaced the cylinder head/head gasket on this same vehicle.

Discuss this DIY here.


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