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The hydraulic system:

Main menu hydraulics
The complete hydraulic system

The Brake system
The height control system

The fluid pressure control
The hydraulic diagrams

 

The brake system:

Introduction
Diagnostics table
Conjunction of components

Components:
   Brake calipers
   Brake distribution valve

 
   Brake pressure limiting valve
   Master cylinder

 

Diagnostics table of the brake system

This page contains a comprehensive table to determine the causes of failures on the hydraulic brake system and the actions that can be taken to solve the problems.

Symptom

Possible cause

Action

Uneven braking resulting in car not stopping in a straight line

1. Tyre pressure incorrect.
2. Incorrect linings on the pads of one or more wheels.
3. Oil, grease or brake fluid on pads.
4. Caliper piston seized.
5. Caliper piston seal seepage.
6. Steering geometry incorrect..

1. Check and correct.
2. Install pads with correct linings.

3. Clean pad linings or replace.
4. Check, dismantle and correct.
5. Renew seal.
6. Check wheel alignment and steering geometry.

Brakes surging on and off while travelling without the pedal being depressed.

Height control system stuck on permanent 'fast'.

Check the restrictor valves on bleed fouling. Test solenoid operation.

Brake application jerky and hard to control; brakes surging.

1. Distribution valve sticking or partially seized.

2. Pedal linkage partially seized or damaged.
3. Sticking caliper pistons.
4. Master cylinder partially seized or blocked.

1. Inspect and test valves for freedom and correct operation.
2. Inspect pedal linkage.
3. Inspect caliper pistons for freedom.
4. Inspect master cylinder and test for freedom and correct operation.

Brake pedal spongy.

1. Air in master cylinder, calipers or feed lines.
2. Swollen caliper seals or hoses due to use of incorrect fluid.

1. Bleed master cylinder and/or brake lines.
2. Check fluid, renew hoses, seals etc.; drain, flush and refill system(s) with correct fluid.

Pedal fails to return to correct 'off' position.

Pull off springs broken or uncoupled.

Check the springs.

Brake pedal travels almost to floorboards before brakes operate.

1. Master cylinder failure or dirt holding cut-off valve off its seat.
2. Leakage in master cylinder rear brake lines or caliper piston.
3. Low pressure of the hydraulic liquid.

1. Check master cylinder for operation. Remove and clean.
2. Inspect for leakage and correct as necessary.

3. Check the pumps and the accumulators.

Brake pedal increased travel.

1. Prolonged or abnormal use of brakes causing brake fluid to boil through being contaminated.
2. Air in the hydraulic system.
3. Pedal linkage incorrectly set.

1. Drain, flush, refill and bleed systems.

2. Bleed the system.
3. Check and reset linkage relative to pedal.

Brake pedal increased travel with warning light on, plus slight decrease in efficiency and slightly heavier brakes.

Failure in the pumps or low pressure in the accumulators.

Check the pumps and accumulators for operation. The gas of the accumulators can have deflated through a leaky membrane or the valves of the accumulators operate incorrect.

Brake pedal increased travel with warning light on, plus marked decrease in efficiency and heavier brakes.

Failure in all brakes system.

Check system for operation.

Rear wheels locking prematurely under heavy braking.

Pressure limiting valve (cf an abs-system) faulty.

Check valve; renew valve.

Brake squeak on application.

1. Incorrectly lined pads fitted.
2. Pads damaged through overheating.

1. Renew pads with correct type.
2. Renew pads.



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