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Brake system leak...looking for part name

2002 Neon, 140K mi.

Step-son complained of “soft pedal,” determined fluid had been run low in one of the two circuits. I replaced both leaking rear wheel cylinders on this car. At the time, couldn’t find any other leaks, and I called it a day.

Today, he came back, complaining of dropping fluid level. Bled system and looked for leaks. As it turned out, fluid was leaking near the master. On this design, there are four brake lines from the MC. On two of the four, there is some form of aluminum nut, with a rubber gasket “sandwiched” in the middle. (This screws into the MC, and the line screws into this nut.) There was a second leak from one of the two rubber gaskets.

So…the MC is (potentially) OK, and auto parts diagrams don’t show these parts. What is this part, and how do I order it? I don’t know what it is, exactly…maybe some weird proportioning valve setup?

(Perhaps in 24 hr or so I can get a photo of it.)

Try proportioning valve o rings, Look like this?

Yeah, that looks like it, but that sure wasn’t what AAP showed!
Looks like this:

It’s squirting out of the larger o-ring. Guess it needs new rubber parts!

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Be sure and use the proper O-ring, NOT just any Buna-N or Nitrile O-ring from the hardware store. Brake fluid will destroy anything but EPDM O-rings. Soak them in a little brake fluid overnight before installing.

Buna-N will swell, EPDM will not.