Guy's, I really did not intend to start an argument at all, and I fully believe GermanStar and everyone else are giving there honest and most believed opinion. It just strikes me as odd that rebuilding a master cylinder seems to have such frightning, serious connatations compared to rebuilding a brake caliper, or replacing flex disks, or meddling with the throttle linkage, all of which could produce an out of control and therefore dangerous vehicle, just as the old master cylinder could do. Discrephencies like that bother me.

I've sold parts, at the worst possible place, the McParts store. I KNOW how often there brake componets come back, those Beck/Arnley or Cardone master cylinders are in and out pretty regular, even when there brand new. Mass produced junk is what they are in general. When I used to need one for someone who couldnt afford the higher priced Bendex(which you at least hope is better) I'd sometimes pull three MC's off the shelf and pull them and watch for torn seals, scored bores, all that stuff is common to find on those "remanufactured" master cylinder they sell at auto zone, advance, partsamerica, CTA, o'rielys, all of them.

So for those of you that are concerned for your safety because one single, solitary man was considering just rebuilding his master cylinder, I want you to think about all of the hundreds of thousands of cars on the road driven by cheap people who blindly buy the $29.95 master cylinder from McParts and merryly toddle on out in life to drive amoung your friends and family with what amounts to sub standard brakeing equipment.
Now think about that real hard, the sheer number of people, and then tell me that a reasonably intelegent man who is willing to take the time to see if the factory quality parts cannot be kept in service safely, tell me that I'm more of a danger than those hundreds of thousands out there.

And too the few votes of confidence, I thank you. This is all just a sadly close to home example of how things are just generaly screwed up in the world. It's not even the big things that really get under my skin, it's little stuff like this.

As for my solution, I am going to go order the $40 McParts MC and see just how they rebuilt this one. If they bushed then re-bored the cylinder I'll have my new piston, or at least seals. If there oversized I'll return it and order the OEM piece. This would all be different if I was keeping this car, but I'm not, it's temporary. If I was keeping it there would have been no question, bills to be payed or no, that I'd have ordered the OEM part from whoever had it cheaper. But this albeit rather nice looking w123 is destined to be someones parts car eventualy.

Oh, and just to bother people more, your aware salvage yards sell master cylinder of cars that are junked..
It would amaze me, I've had people come in and buy rubber brake hoses off twenty+ year old vehicles.
Life really is a risk. Every single day.