brake master cylinder

I'm having quite a problem with master cylinder on my forklift. There just are not that many parts. Two 3/4 inch cups, one check valve, the piston and the spring. Finally a flat washer and the snap ring. Only one pressure line going out of this thing. And one port coming from resavor. Can someone tell me the order of assembly? Which way does the check valve go? I took it apart because the pedal would slowly collapse when applied. Saw that one of the rubber cups was scored. Got new cups and honed the cylinder but now cannot get it to build pressure.

Should be a do-nut-like rubber ring that goes in first, then the residual pressure valve (which probably snaps into the end of the spring), then the open side of the cup followed by the piston, then flat washer and snap ring.

The "residual pressure valve" flows fluid freely in the "apply" direction, then acts a a check in the reverse direction, fluid has to flow between it and the rubber "do-nut" ring as it returns, keeping a small residual pressure on the wheel cylinder cups to lessen the chnace of leakage between brake applications.

If it was working before, but just bypassing, it may just have air in the system.

If you replaced the piston, check it carefully against the original. It must be exactly the same length. Also check the depth of the rod hole, length of the spring.

The piston must return completely when released. Be sure it does return, as in the spring returns it, and the pedal rod lets it return when released.

The pressure cup (the first one in), the lip end goes in first, the flat side against the piston. Some use a metal expander that sits between the spring and the cup.

The second seal ring (the last one in), the lip side goes in first.

I like to bench bleed first. Fill it with fluid, hold your finger over the outlet, push the plunger in, using your finger as a check valve to let fluid out, but not let air in. Keep bleeding and watching the reservoir until no bubbles are coming up.

A side note, when you cleaned and honed, what did you wash it out with? If you used petroleum based solvent, it may have swelled the rubber cups. Use only non petroleum solvents, like spray carb cleaner, lacquer thinner, alcohol, etc. If it was cleaned with petroleum solvent, it will need to come apart, be cleaned, and new seals.

Did you try to find a new complete cylinder? There is a casting number, many lift truck parts suppliers online. You'd be surprised what's still available for some of the obscure lifts out there!
Cylinder Diagram

Thanks, I don't understand the function of the check valve or which direction it goes. Or even where it goes. I am using same piston and washed it out with brake fluid.

In the diagram link, the check valve is referred to as the "inlet valve".

It typically snaps into the end of the return spring and seats against a rubber washer down in the end of the bore.

It is not a necessary part in order to function. It's purpose is to help retain just a little positive pressure in the lines between uses to help keep a higher pedal. If the shoes are adjusted correctly you won't miss it.