Bench Bleeding Question

I am trying to get all the air out of a dual master cylinder. It is a used unit that came with a project car. Mid 80's S10 master cylinder. Did a search and didn't find what I need. I am using hoses returning fluid to the reservoirs. I have one that instantly started pumping air out of the bottom orifice. Got all the air out of it, but the other one is only pumping fluid out of the return hose, not the bottom orifice. I am pressing the cylinder in about a inch with each stroke. Should I be seeing air and then fluid coming up out of both orifices? Thanks

 

Why don't you full stroke it and see what happens.

 

As V8 Bob said full stroke will get it all out.

 

I have the master cylinder setup in a vice. I am pressing the back with a rod. I am only getting about a inch travel. Is that the problem?

 

I am actually getting about a 1 5/8 stroke. It feels bottomed out at that point. Still only getting fluid coming through the hose to the reservoir on one. Nothing coming up from the bottom. This is a used piece and I am wondering it it is bad?

 

I would NEVER install a used brake cylinder - master or wheel - without a complete rebuild. That fluid is hygroscopic (attracts/absorbs water/moisture readily). This will allow it to permeate a brake system and collect/settle in cylinder bores, corroding the walls. That corrosion will tear the rubber seals.

Take it apart, install a complete rebuild kit (hone if necessary), then do your bench bleeding.

dj

 

I prefer pressure bleeding. get a spare master cyl cap and drill it out and weld an air fitting to it and hook up a pressure regulator from a paint gun and an air hose and run it at about 10 psi and you can bleed your whole system in seconds with no pedal pumpin "hold it, pump it, hold it" B.S.

 

Gave up. Just picked up a rebuilt.