power brake booster check valve

Ok , the valve is not the problem. It may or may not be defective, but that's not the source.
So now we need to determine if the booster is bad or if there exists a brake problem, or if the booster pushrod needs adjusting.
Next question, takes us back to post #2; Has the booster ever, in the recent past, provided assist? Or is it a recent transplant? When the pedal gets hard, is it at the top of it's stroke or somewhere halfway down.Depending on the answers to these questions, will lead us to the next logical, test. But I'll skip ahead anyway.
-The brake pedal should not be hard at the top of it's stroke, especially if the car has 4 drums on it. If it gets hard right away, the pedal cannot activate the booster. The pedal has to travel downwards some to activate the booster.
-Let's assume the pedal travels downward to around 50 % of its travel, and that no wheel cylinders are seized, and that the compensating port in the bottom of the master cylinder is open and functioning, so that the brakefluid is returning as would be normal.Now, that's a lot of assuming.
So that takes us to the booster.If you were to pull the booster off the firewall, you would see a linkrod in there, connecting the brake pedal to the booster guts. This rod has to be just the right length, to transmit the pedal motion to the booster valve, at just the right time and amount, to provide the assist.If it is too short you get no boost. If it get's to be too long the boost will be too much, and too early, making smooth stops very difficult.If it's really, really too long, there's a good chance it will brake the internal valve, rendering the booster junk.
-So that take's us back to the questions. If the booster was working recently, and just suddenly quit, well that would rule out the pushrod length.
-But if it's a recent transplant,not so. An adjustment, or several, may awaken it.
-Now lets get back to the assumptions.If the pedal get's hard at the top of it's stroke, lemme know,and I'll get into that.