[ProwlerGT]

Well for future readers here's some interesting detail on the push-rod:

The summary:
It may be wise to readjust your power booster push-rod cap nut +/- every 50k miles depending on driving habits. It may also be a good practice to put a 7mm nut behind the cap nut so that it does not move in the future thereby eliminating the need for future adjustment after much use.

The details:
That 3/8" I wrote about ... well I believe I've figured out where I lost it. The little cap nut that is the tip of the push-rod that pushes the master cylinder is almost exactly 3/8" long. It is actually about 6.5/16 long which comes to 3.25/8" long.

Whats this mean? Before the fluid in the reservoir moves (top of reservoir off pushing pedal ever so slowly) the pedal travels 3/8" down. The cap nut is adjusted or I should say PUSHED BACK OVER TIME DUE TO USE 3/8" back and thus the delay of braking and loss of ability to use fully available brake power.

Each successive push of the brake pedal moves the cap nut EVER EVER EVER EVER EVER so slightly backwards in a clockwise motion due to sheer forward pushing force. Over many thousands of miles; probably over 60k the cap nut gets far enough back to where it affects the braking performance.

I found this stuff out I went to adjust the cap nut on my old OEM booster which is off the car. The cap nut would not budge at all. It was jammed all the way back and I had to use the vice grip pliers to hold the rear grip portion in place while i turned the cap nut counter-clockwise.

The only thing that bothers me though is if the cap nut is 3/8" long and the brake pedal engages the fluid movement at 3/8" push down then this would mean adjusting the cap nut outward nearly its full length, which I believe would damn near push it right off the end of the push-rod threads. Though on the car vs using the spare I had to work on may make a difference since its all connected up to the pedal etc.. Though I also have to see the back of the master cylinder push plate too and see if it is worn inward though that would've been taken care of during the mc rebuild I do believe.

Idea: A 7mm nut behind the push-rod cap nut tightened good against it may eliminate the need for future adjustment.

I haven't been able to will myself to work on the car yet cause I don't want to set myself up for further disappointment even though I'm confident about this fix, but now having done this on the spare booster I've got some reference experience for doing it on the car.