'85 300D - leaky rebuilt caliper from NAPA
 

I put on rebuilt calipers all around, and when I pumped up my pressure bleeder, I noticed a drip coming from the right front. All 4 bleeder screws were closed. It appeared that it was coming from the inside piston.

I went ahead and bled the system, and then pumped the brakes. The leak seemed to slow down then stop.

I'm thinking that the rubber seal just had to seat. I have placed cardboard under it so I can see if it leaks overnight.

Should I just pull this caliper and return it (rather not have to do that), or try it for a while and keep checking?

You have no idea why it is leaking. It is not supposed to leak. Things don't usually fix themselves or last long when they do. I would take it back. You don't want to keep messing with brakes when they are supposed to be fixed. Finish the job whatever it takes and be done.

I always buy remanned calipers locally because of not wanting to pay shipping when things like this happen. Change your hoses if they show any signs of cracking so you don't have to deal with them later. It is a good idea to keep your cores until you know the new part works well.

Not particularly helpful at the moment, but: I like to do my own rebuilds for precisely this reason. Cheaper in parts - sure, expensive in time - but so worth it to know what you got...

FWIW, by way of input? : I've long ago replaced all the rubber brake hoses on my '83 - and last year replaced all the steel lines as well. You may be at, or nearing, this point.

just curious, were your NAPA sourced calipers ATE or Bendix? And were they in boxes that were branded "Eclipse?"

Well, as it turns out, I'm a big dummy.
The caliper is just fine. I had replaced the flex rubber lines all around and I had not done the final tightening on this one, and that is where it was leaking.
So- all is well. Sorry for the fake news. :)

They are Bendix, BTW.