Toyota Hilux Surf 1993 Owner's Manual page 699

BR–66
BRAKE SYSTEM – Load Sensing Proportioning and By–Pass Valve (LSP & BV)
(b) In event the pressure cannot be adjusted by the
No. 1 shackle, raise or lower the valve body.
Low pressure – Lower
High pressure – Raise
(c) Torque the nuts.
Torque: 13 N–m (130 kgf–cm, 9 ft–lbf)
(d) Adjust the length of the No. 1 shackle again.
If it cannot be adjusted, inspect the valve housing.
6. IF NECESSARY, CHECK VALVE BODY
(a) Assemble the valve body in the uppermost position.
HINT: When the brakes are applied, the piston will
move down about 1 mm (0.04 in.). Even at this time, the
piston should not make contact with or move the load
sensing spring.
(b) In this position, check the rear brake pressure.
2WD (SRW)
4WD (DRW)
4WD (Regular cab)
4WD (Extra cab)
If the measured value is not within standard, replace
the valve body.