Pickup 4WD L4-2559cc 2.6L SOHC (4ZE1) (1988)
Brake Proportioning/Combination Valve: Description and Operation
These valve(s) which are threaded into the master cylinder (standard brake system), limit outlet pressure to the rear brakes after a predetermined
master cylinder pressure has been reached. This is used when less rear apply force is needed to obtain optimum braking.