Opel Frontera UBS. Manual - part 1106

POWER ASSISTED BRAKE SYSTEM  5C – 29

P & B VALVE REPLACEMENT

1

3

1

  

2

Removal Steps

1.

Hydraulic pipes

2.

Bolt

3.

P & B valve

Installation Steps

To install, follow the removal steps in the
reverse order.

REMOVAL

•

P & B valve is not repairable and must be
replaced as a complete assembly.

•

Care must be taken to prevent brake fluid from
contacting any painted surface.

1. Hydraulic Pipes

•

Plug the pipes to prevent the loss of fluid or the
entrance of dirt.

2. Bolt

3. P & B Valve

INSTALLATION

3. P & B Valve

2. Bolt

Bolt Torque

N·m(kg·cm/lb·in)

13 (130/113)

1. Hydraulic Pipes

Hydraulic Pipe Torque

N·m(kg·m/lb·ft)

16 (1.6/12)

After installing the brake pipes, bleed brakes as
described in Bleeding Brake Hydrauric System this
section.

5C – 30 POWER ASSISTED BRAKE SYSTEM

LOAD SENSING PROPORTIONING VALVE (LSPV)
(FOR EUROPE AND SOUTH AFRICA)

to rear wheel cylinder

from front master cylinder

from rear master cylinder

Structure and Operation

The following is an explanation of the structure and
operation of the linkage 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 lever and a
valve.

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

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POWER ASSISTED BRAKE SYSTEM  5C – 31

•

Operation

1) Outline

When the L.S.P.V. (Load Sensing Proportioning
Valve) detects a change in load weight, the load
sensing lever moves. Its reaction force is
transmitted to the bottom of the load sensing
valve to secure an optimum rear wheel cylinder
fluid pressure break point in proportion to the
actual load weight.
Besides, if the front brake system should fail, the
devices is designed to prevent the master cylinder
fluid pressure from decreasing and to apply it
directly to the rear wheel cylinder to obtain a
sufficient braking performance.

From rear
master cylinder

2) Operation

(1) When the fluid pressure is under the break point.

The fluid pressure of the rear master cylinder
passes through a clearance between the valve
seal and the piston and acts on the rear wheel
cylinder. At this moment, a downward force is
applied to the piston. However, the compression
spring force and reaction force of the load sensing
lever keep the piston in the upper position by
pushing upwards. (See the left figure.)

To rear
wheel cylinder

(2) When the fluid pressure is equal to the break

point.
As the rear wheel cylinder pressure increases, it
surpasses the compression spring force and
reaction force of the load sensing lever, causing
the pistion to move downwards, so that the
pistion butts against the valve seal to shut off the
fluid line between the master cylinder and rear
wheel cylinder. (See the left figure.)

(3) When the fluid pressure is over the break point.

When the fluid pressure increases further, the
piston moves upwards. The moment the piston
comes apart from the valve seal, fluid pressure is
applied to the rear wheel cylinder and the piston
moves downwards so that the fluid line is shut off
again. This process goes on repeatedly to control
the fluid pressure to the rear wheel cylinder.

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5C – 32 POWER ASSISTED BRAKE SYSTEM

(4) When the front brake system fails.

When there is a failure in the front brake system,
the fluid pressure from the front master cylinder
decreases. As a result, the balance between the
front and rear brake side fluid pressures is lost at
the control valve sleeve so that the control valve
sleeve moves upwards.
The control valve sleeve strikes against the piston,
thereby pushing the piston upwards.
Accordingly, the fluid pressure of the rear master
cylinder is not decreased and is applied directly to
the rear wheel cylinder to secure a sufficient
braking performance of the rear brakes. (See the
left figure.) 

Valve Maintenance
In the case of fluid leak or other abnormalities, faulty
valve should be replaced.

Note:
The load sensing proportioning valve is not
repairable and must be replaced as a complete
assembly.

ADJUSTMENT PROCEDURE OF LSPV

1. Adjust the rear axle weight by loading the

laggage compartmemt as necessary.

Rear Axle Weight

N (kg / lb)

10,300 (1,050 / 2,315)

Note:
The rear axle weight should be adjusted to the
specified value with a man seated in the driver seat.

Rear master cylinder
fluid Pressure

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