I've seen all the posts/debates about the risks involved with using rebuilt master cylinders, but never heard of any actual cases where anyone ever ran into any trouble. So I went with a rebuilt. However I noticed this divot in the metal near the o-clip on the rebuilt unit. Should I be concerned about it? I figure not, as it's not a seal, but thought I'd get some other opinions.

Also the push rod was locked into the old MC, but no way to lock it into the rebuilt unit. Does it matter? Any chance the rod could come out of the MC? Obviously that would be a problem, but not positive since the push rod would seem to be secure despite being locked in. Your thoughts?

Thanks,
Mark

Is that a divot or is it extra (raised) metal? In the picture it looks like just an extra piece of metal leftover from the casting or something. I would not suspect it would be an issue-- is this a brake or clutch MC? I don't think that it matters that it doesn't lock in as the pressure from the other end will keep it from backing out.

Good question - maybe it was added during the rebuild for some reason. How about the push rod not locking in - issue?

The push rod on my clutch MC doesn't lock in place and hasn't been an issue. I suspect you're fine.

another question: how tight should I screw on the MC lines to the copper block that leads to the brakes? Sorry, don't know the proper terminology for parts. It's pretty tight, don't want to over tighten, but definitely don't want it to come loose.

You shouldn't need to tighten beyond snug. Brake fluid tends to almost corrode itself tight.

Tighten until it doesn't leak