1975 Datsun 280z FSM - Spooled up Racing

Brake System
Master cylinder
front side
Master cylinder
rear side
BR 622
To front wheel cylinder
3)
To rear wheel
cylinder
1 O-ring
2 Plunger
3 Back-up ring
4 Y-seal
5 Lip seal
6 Spring
7 Valve body
8 Spring retainer
9 Cup seal
10 O-ring
NP-VALVE
This valve controls the pressure of
the rear wheel cylinder to prevent the
earilier locking of the rear wheel. The
valve serves as a mere connector earlier
locking of the rear wheel. The valve
serves as a mere connector independently
of the rear system.
When the front brake is leaking, the
split point becomes much higher. This
causes the rear brake to behave as if it
were without the NP-valve.
S
o
"So
Fig. BR-8
Cross-sectional view of NP-valve
Note: Split point of NP-valve characteristic
curve differs for S30 and
GS30 models.
OPERATING TEST
0 200 400 600 800 1,000 1,200 1,400
Master cylinder side oil pressure (kg/cm 2 , psi)
BR623
Fig. BR-9 NP-valve characteristic curves for S30 model
Conduct the following periodic test
at specified interval.
At the test, place the car on dry
concrete road with only driver laden
and apply a sudden brake at 50 km/h
(31 MPH).
1. NP-valve functions normally
when rear wheels lock simultaneously
with front wheels lock ahead of rear
wheels.
2. If the rear, instead of front,
wheels have locked in advance, it may
be attributable to malfunctioning of
NP-valve. Replace NP-valve with a new
one as an assembly.
Note: When this test is conducted,
pay attention to other cars.
REMOVAL AND
INSTALLATION
NP-valve can be removed easily by
removing installation bolts. When installing,
however, note the following:
200 400 600 800 1,000 1,200 1,400
Master cylinder side oil pressure (kg/cm 2 , psi)
kg/cm 2
psi
BR679
Fig. BR-10 NP-valve characteristic curves for GS30 (2+2 seats) model
BR-6