2007 ISUZU KB P190 brakes

5C-18 BRAKES
BRAKE LINES (HOSES AND PIPES)
(MODEL WITH ABS)
N ⋅m (kgf ⋅m/lb ⋅ft)





This illustration is based on the RHD model

RTW 75CLF000301



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ISUZU KB P190 2007

BRAKES 5C-19
SERVICING
BLEND PROPORTIONING VALVE (IF SO EQUIPPED)





Structure and Operation
•
••
•
Structure
Side
a shows P-valve; side b shows bypass valve.
Bypass valve seals the routes
4 and 5 using the seal 2at
the piston
1 end.
In addition, spring
3 presses against the piston 1, and in
order to seal out the route
4 and route 5 sufficiently, spring
3 presses seal 2 against cylinder end surface.
The left figure is a characteristic curve diagram.


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ISUZU KB P190 2007

5C-20 BRAKES

•
••
•
Operation
The operation of the P-valve by the master cylinde
r
pressure is unchanged up to the brake points
A and B.
If master cylinder fluid pressure penetrates into the second break point
B, the fluid pressure pressing against the seal
, (which isolated route 4 and route 5), passing the route
4of the master cylinder side, overcomes the operating
force of the spring
3 + fluid pressure affecting the seal 2of
the wheel cylinder, and presses the piston
1to the right
side, resulting in the opening of the routes
4 and 5, and
canceling of the P-valve operation.
Then, because the master cylinder fluid pressure and the wheel cylinder fluid pressure, up to the point
C, operate on
the identical surface of the seal
, both have identical
ascending ratios.
However, because of the operation of spring
3in the wheel
cylinder side, wheel cylinder fluid pressure operates to
preserve the balance against the master cylinder fluid
pressure on the lower level with the difference in pressure
resulting from this spring.




RTW 75CSH001601

Valve Maintenance
In the case of a fluid leak or other abnormality, the faulty valve
should be replaced.
The valve is set up at the engine room.
Note:
The blend proportioning valve is not repairable and must
be replaced as a complete assembly.





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BRAKES 5C-21
LOAD SENSING PROPORTIONING VALVE (LSPV)
RTW 35CMF000101



Structure and Operation
The following is an explanation of the structure and operation
of the spring type load sensing device.
This device controls the fluid pressure to the rear brakes in
accordance with changes in rear axle load (vertical
displacements of the rear axle springs).





•
••
•
Structure
This device consists of a load sensing spring and a valve.
The valve is mounted through a bracket to the frame.
One end of the load sensing spring is fixed to the valve at the frame and the other end to the rear axle housing
through a bracket.


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5C-22 BRAKES
RTW 35CSH001001

•
••
•
Operation
1) Outline
W hen the LSPV (Load Sensing Proportioning Valve) detects a change in load weight, the load sensing spring
stretches.
Its reaction force is transmitted to the bottom of the load sensing valve to secure an optimum rear wheel cylinde
r
fluid pressure break point in proportion to the actual load
weight.
Besides, if the front brake system should fail, the device is designed to prevent the master cylinder fluid pressure from
decreasing and to apply it directly to the rear wheel cylinde
r
to obtain a sufficient braking performance.

RTW 35CSH001101

2) Bellow cutting point.
The Force (F) keeps the main piston (1) the rest position. The inlet pressure (A) and outlet pressure (B) are the same
as well as the inlet pressure (C) from front master cylinder.
The bypass piston (2) is kept on rest position by equilibrium
of the pressures (A) and (C) and the bypass spring load (3).

RTW 35CSH001201
3) Cutting point.
The cutting point is given by relation between force (F), that is the load applied by suspension of the vehicle and the
main piston area (1). The cutting point is achieved when the
force generated by hydraulic pressure is upper than the
force (F) given by the load suspension. The main piston (1)
moves from the rest position closing the valve. In this
moment the inlet pressure (A) is upper than the outlet
pressure (B). The bypass piston (2) continues on the rest
position by equilibrium of (A) and (C) pressure.


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ISUZU KB P190 2007

BRAKES 5C-23
RTW 35CSH001301

4) Failure on front master cylinder.
In case of failure on front master cylinder the pressure on the inlet port (C) drop to zero. The pressure from inlet port
(A) acts on the bypass piston (2) and move it by comprising
of bypass spring (3). It makes possible the communication
between the inlet port (A) to outlet port (B) through the
bypass system. The outlet pressure (B) reaches the inlet
pressure (A) and the LSPV is bypassed.


Valve Maintenance
In the case to fluid lead or other a abnormalities, faulty valve
should be replaced.
Note:
The load sensing proportioning valve is not repairable and
must be replaced as a completed assembly.


LOAD SENSING PROPORTIONING
VALVE (LSPV) ADJUSTMENT
RTW 35CSH000301
1. Fluid Pressure Measurement
1) Rear axle weight adjustment
W ith an axle weight meter, adjust the rear axle weight with a person sitting in the driver’s seat and a weight
loaded in the rear body. N (kg/lb)
MODEL Adjustment value
4 × 2 7845 (800/1764)
4 × 2 HIGH RIDE
4 × 4 9316 (950/2095)

RTW 35CSH000101





2) Installation of a fluid pressure gauge
Remove the air bleeder of the left hand wheel front and rear brakes. Bleed air out of the fluid pressure gauge
with the measurement hose of the fluid pressure gauge
installed.
Pressure Tester: Brake oil (Fluid pressure gauge)
5-8840-2190-0

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5C-24 BRAKES
RTW 35CSH000201
3) Rear wheel cylinder fluid pressure measurement
Step on the brake pedal until the fluid pressure of the front wheel cylinder gets to 9.8Mpa (100kg/cm
2), and
check the rear wheel cylinder fluid pressure. (Read the
value of the front wheel cylinder fluid pressure 2
seconds after the measurement. W hen measuring the
LSPV fluid pressure, keep the brake pedal pressed
down without stepping it down twice or releasing it.)
Rear W heel Cylinder Fluid Pressure MPa (kg/cm
2)
2W D 6.77 ±0.83 (69.0 ±8.5)
2W D (W ith High Ride
Suspension), 4W D 6.77
±0.83 (69.0 ±8.5)

RTW 35CSH000401
2. Oil Pressure Adjustment
1) LSPV spring length adjustment
Loosen the adjust nut of the LSPV spring joint, and adjust the length of the LSPV spring.
W hen the oil pressure is insufficient, turn the adjust nut clockwise to extend the span “A”. W hen the oil pressure
is too high, turn the adjust nut counterclockwise to
reduce the span “A”.


2) After adjustment, tighten the lock nut securely.
Lock Nut Torque N⋅m (kgf ⋅m/lb ⋅ft)
11-20 (1.1-2.0/8-14)


















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BRAKES 5C-25
Filling Master Cylinder Reservoir
CAUTION:
Use only specified brake fluid. Do not use any fluid which
contains a petroleum base. Do not use a container which
has been used for petroleum based fluids or a containe
r
which is wet with water. Petroleum based fluid will cause
swelling and distortion of rubber parts in the hydraulic
brake system. Water mixed with brake fluid lowers the
fluid boiling point. Keep all fluid containers capped to
prevent contamination.
Always fill the master cylinder reservoir when the engine
is cold.
Never allow the brake fluid to come in contact with the
painted surfaces.
The master cylinder reservoir must be kept properly filled
to ensure adequate reserve and to prevent air and
moisture from entering the hydraulic system. However,
because of expansion due to heat absorbed from the
brakes and the engine, the reservoir must not be
overfilled. Thoroughly clean reservoir cap before removal
to avoid getting dirt into reservoir. Add fluid as required to
bring level to the “MAX” mark on the reservoir tank. Use
“DOT 3” Hydraulic Brake Fluid.

Leakage of Brake Fluid
W ith engine idling, set shift lever in the neutral position and
continue to depress brake pedal at a constant pedal
application force.
Should the pedal stroke become deeper gradually, leakage
from the hydraulic pressure system is possible.
Make sure by visual check that there is no leak.




BLEEDING OF THE BRAKE HYDRAULIC
CIRCUIT
If air enters the bake lines, it will cause poor brake action.
Therefore, bleeding should be performed if the brakes have
been used with the level of brake fluid in the reservoi
r
excessively low or if brake pipes have been disconnected in
the course of brake servicing.
The bleeding operation calls for co-operative action of 2
persons.
• Set the parking brake firmly while bleeding.
• Perform bleeding operation with ENGINE RUNNING, to
prevent damage to push rod seal.
Make sure exhaust is suitably ventilated.
• Bleed the hydraulic system with the fluid reservoir filled to
the specified level.
• Bleed the system starting with the rear wheel cylinde
r
farthest from the master cylinder.


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ISUZU KB P190 2007