Brake reservoir is filling up in front and draining in rear

[candymancan]

So since day one this brake reservoir on my 76 j10 ( which was replaced in 2006 and the brake lines to the rear) avcording to paper work. Its got a large reservoir in front. Small in rear. I fill the rear.. and it goes empty after a 20 mile drive. And the front one actually fills up more. Refill.. front fills up more till i gatta start sucking the fluid out and putting it in the rear.

Ive already bled the system and got the nasty stuff out. But it still does this. Why ? And no it isnt leaking. The rear is filling the front up as i drive. Trust me im under this Jeep a lot.. there are 0 leaks on the rear drums. And the line is brand new. Well newer.. its stainless and got 0 rust. The front is rusty original

[SJTD]

Seems to me the master has to be leaking between the pistons.

[candymancan]

Well nothing is leaking visually on the drums at all i took them off.. followed the metal line all the way up to the master cylinder. No leaks. BUT Thr main reservior is getting filled as the rear drains.

Do both reserviors connect inside somehow ?

Is it like this ?