William,
My father was a mechanic, also. I began working on cars when I was in Junior High, nearly 60 years ago. It would be interesting to know how many of the people participating in this forum had fathers who were mechanics.

Larry (Delor) is right, of course. The calipers should be replaced in pairs. Whether you want to replace all four is a matter only you can decide. How long do you plan to keep the car? How much do you use it? Would a failure at some unforeseen time in the future likely cause you a lot of inconvenience? Etc.?

My guess would be that the master cylinder has sustained some damage from maintenance neglect. You may want to dismantle it, check it out and put a repair kit in it if you find it is not too bad. I had to rebuild mine(right after the car got out of its one year warranty ) and found it very easy to do. It has now lasted about 20 years without further trouble.

Good luck with whatever you decide.



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Ted
1979 240D
160,000 miles