How many of you have keys that are interchangeable between 2 cars?
Well, I do. The key from my recently acquired 83 240D fits some of the locks (door and ign but not the trunk) in the 300D and vise versa. The keys are not identical in cut and do not fit perfectly in either vehicle but a second or 2 of jiggling will open it. I suppose there is a lot of slop in the key and lock due to wear.

The 240D trunk lock takes about 5 minutes of jiggling to open PITA. I got tired of it and took the tumbler out and found 2 wafers sticking up too much. Probably the wrong key? I did the easy fix which is to pull and eliminate the 2 offending wafers (and spring), now the key works perfectly. There was an amber color rubber seal that was broken into 2 pieces and I left it out. There was also a pot metal ball and sping detent for the tumbler which needed a special tool which I did not have so that was left out also. The lock/key works fine otherwise.

I am going to pull the other locks and get them to work better. A key should open the lock immediately without jiggling.

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85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked