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I have a hard question. I rebuilt my power booster brake on my car and as we were completing the process we noticed that inside on the cylinder that slides up and down the vacuum canister, it had two small valves on the disk that lets air go either in or out of the vacuum canister. When we took it apart one of the little circular valves was off..or loose in its seat. We found the necessary clip or push on washer to put it back in place however if that clip is put on then since it is on a rocker arm the other little circular valve seat stays open all the time and one is closed. If the one that is closed is pushed open the opposite circular seal that is already open, opens even more, that one never closes. Does anyone have a detailed plan of how that cylinder works with letting air in and out of the brake canister to assist brake cylinder sliding back and forth? Here is a video of what I am talking about. help.dropbox.com/s/vhoc495u4zhwm6n/20150905_211817.mp4?dl=0

You are headed in the right direction but have missed one thing. There is nothing wrong with your assembly as shown and you should go ahead and put that little clip back on as long as you are sure that the rubbers on those little poppets are in good shape and that they swivel on their little stems as they should.

What you have missed is that as the pushrod from the pedal slides through the casting it will move the "teeter-totter" up away from the casting. This will cause the poppet valve under the bronze spring to open and the other one to pull closed. Thus the vacuum side of the power piston is at once closed to the atmosphere and opened to the vacuum source. When you release, the big spring that is under the diaphragm will raise the push rod back through the casting and the position of the teeter totter will reverse opening to atmosphere and closing to vacuum.

So I guess you need to make sure that the pushrod is moving relative to the casting. In the film I saw some sort of goober around it that made me wonder.

Ross, thanks for the reply. Are you saying that when I push the brake pedal, the rod is not only supposed to push the entire disk(with the leather around it), but that just before that, the rod itself slides a tiny bit through the disk before it start actually pushing the whole disk down the cylinder? In order words, the rod slides back and forth a tiny bit... or are you just saying it is supposed to able to move side to side (I removed that goober around the rod, which was a rubber o-ring I thought went there, but after looking at the video of when I removed it, it was not there, so I removed it and now the rob moves in a circular motion, but does not push "through" the disk (casting, I think you called it.)

The center plunger needs to move in the casting. How else would it activate the valving? Yours has probably seized up. Remove the clips from the poppets and the bronze leaf spring. You can then tap the pushrod and the plunger with the teeter totter out of the casting clean it up, and lubricate it with some silicone grease.