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I am bleeding my master cylinder while installed in the car. The power brake unit is from a 280zx 2+2 and is approximatly 10.5 inches in diameter. I've run a clear plastic tubing from each master cylinder bleed port to its corresponding fluid reservoir. I've filled each with DOT 5. After two strokes pushing air, the front reservoir has a complete cycle: fluid enters the tubing and on the second stroke completes the circuit and re-enters the reservoir. The back reservoir is different. On the first stroke fluid fills the tubing to almost the level of the loop back into the reservoir. However, upon releasing the pedal, the fluid immediately returns to the master cylinder, leaving nothing in the tube. On the next stroke, the fluid from the back reservoir will elevate in the tube; but, then immediately return to the master cylinder. The brake pedal has a distinct feel to it: It has a 1/4 inch of free travel before it engages the master cylinder. Once engaged there is a smooth transition (with a tad of resistance) throughout the stroke until the very end. At stroke's end there is a distinct "click" both felt and heard. The pedal returns to the up position easily and smoothly. This master cylinder was purchased new several years ago and was filled, briefly, with DOT3 before it was removed, drained, and stored on a shelf in my storage unit. I carefully measured the brake rod length on the bench with the vacuum unit out. I "think" that dimension is ok. In terms of troubleshooting, what should be my next step? I have another new 280zx ('83) that looks the same; but, the mounting ears are horizontal rather than vertical. Is the later unit a "bolt one"? Regards, z