Just want to share with you my experience with my 1996 S420. It started with not being able to turn and remove the key in the ignition. I was finally able to get the key out by jiggling and turning the key. I removed the tumbler assembly and noticed that the brass inserts were protruding. I ordered the tumbler part number 140-460-1604 from the dealership with my registration copy. The dealership received mislabeled part. It had the right part number on the packaging but had a tumbler for a 1995 model. It was reordered again and got the same results. The MB dealership said that they cannot get the part for me. I ordered the part for FCP Euro and their website listed the part. I got a call back and they said that the dealership would not sell the part to a third party. If I buy the part from the dealership, they have to install the assembly. I ordered the part from Pelican and their website also listed the part. They emailed after a couple of days that the dealer will not sell the part to them for the same reason. I asked both parts store why the part number is listed from their catalog and they cannot even sell it. They said it was an error and will remove it from the catalog.

Since I cannot get the tumbler through normal channels, I filed the brass key inserts and got them flush. I am able to turn the ignition normally and in the process of doing it, the steering assembly locked out on me. I can start the car but cannot turn the steering. I checked the forum and read some horror stories about this. I read a suggestion about drilling a hole in the lock assembly and inserting a pin to unlock it. It did not work for me. I was able to remove the whole assembly patiently. I did not want to spend more money on this project and I decided to grind off the protruding lock to disable the steering lock system. I assembled it back and it worked. I was able to start the car turn the steering.

Then another problem popped up. The buzzer was going off if I remove the key. It goes out when the car is running. The door switches were fine. This is the same reason why I wanted to change the tumbler assembly to get rid of this nagging noise. Maybe since the tumbler assembly is worn out, it is causing the buzzer to go off even when the key is pulled out. Since I did not get any help from the dealership and some parts dealers, I disabled the buzzer system. I unplugged it and not the car is now quiet. I have been driving the car with no negative effect except there is no buzzer warning on some of the systems (lights on warning, etc).

I still need the tumbler replaced because it is just a matter of time when the tumbler and key wears out and I will be in the same predicament. Sorry for the long post and I just want to share my experience in case someone out there have the same problem.