I have T100 brakes and a dual diaphragm booster on my 87 4Runner along with a manual proportioning valve. It brakes excellent but doesn't start to grab until I press the pedal down an inch or so. The FSM calls this brake pedal free play.

The procedure according to the FSM is to pump the brakes with the engine off to get rid of vacuum for a firm pedal. Then depress the brakes and note where you start getting resistance. I measure 1-1.5" which is too much. The FSM says 0.1-0.25" is within spec. The FSM doesn't give specific directions on how to correct it, just "adjust as necessary".

My question is on how to adjust it. Do I loosen the jam juts on the brake pedal bracket and spin the booster push rod? It seems all I am doing is adjusting the brake pedal height, not adjusting the freeplay.

Any tips?

 

That is the only adjustment you can make.

Unless of course if the rear brakes are so far out of adjustment that is where all your travel is.

You are changing the the length of the linkage moving it closer to the master cylinder piston.

Go to far and the system is under pressure

 

There is also an adjustment for the pushrod on the booster itself. Of corse there is a SST for it. and it needs to be adjusted to 0mm.(zero clearance).
brakeboo.pdf