I just replaced my master cylinder and the power
booster (the mc had been leaking into the
booster for quite a while).

I tried to adjust the length of the push rod
(on the booster) to match the length of
the old one. Is there a way to test if the
current length of the push rod is correct?

The Factory Manual mentions a gauge
(part number 49-8002-765). Is there a way
to make make one of these?

I'm asking because my brake pedal goes
soft when I start the car but it grabs the
brakes when start to feel pressure.

Thanks for any suggestions.

 

The pedal going soft is the booster working. I guess thats what you mean by soft. Not soft like going halfway to the floor. If its soft like that, you have air in the lines or the rear brakes need to be adjusted. (if drum)
About the grabbing. Does it grab like it feels ok and its grabing and stopping. Or grabbing like suddenly. and you have no control.
I have had this problem with a crx. i replaced the booster with another and the new rod. When I test drove, the front rotors were not letting go. They would keep the pressure on the rotors. I had to grind down the new rod to let the MC cylinder come back into the bore. Come to find out it was the wrong booster. After going through all that trouble. I kept it. It worked fine after grinding the rod.
Hope this helps. If not.......give more info.

 

It's grabbing and locking the brakes.

Which, I take to mean that the part of the mc
is working correctly and part still needs air
bled out.

 

Do you have drum or disc in the back?

 

This is an 84 GS with the drums in back.

I re-bled everything this morning. The pedal was still
squishy so I adjusted the push rod so it would stick
out a bit further. That seemed to help a bit. The brakes
don't grab as bad but the pedal is still squishy.

I've bled this thing from top to bottom 5 times, and it
doesn't seem to make a difference.

 

Did you bleed the master cyl before you put it in the car? Loosen the 2 lines going into the master cyl. Have a helper push the brake pedal down and hold it. Tighten the lines. Then have your helper let the pedal go up again. Repeat untill your sure no air is comming out. On the last push, do it slow to give you time to close the lined while pressure is being excerted. Keeps the air from being sucked back in. Then start at the furthest wheel away from it. Bleed all 4 wheels working your way in.
If you still have air, its being sucked in from a wheel cyl or somewhere. Make sure they are not leaking.

 

if you don't bench bleed the MC, it will have air in it, and could be hard to get out after install, depending on the angle of it and the car, and the location of the brake lines (I don't recall exactly what all this is like on a 7, but on my 'yota it has to be bled outside of the truck for it to get all the air out...)

if you have to adjust the pushrod way out, there's definately air or something else wrong with the system...