Power assisted rack and pinion steering system

Diagnose and repair light vehicle steering systems

AURLTD004

This unit describes the performance outcomes required to diagnose and repair faults in the steering systems of light vehicles. It involves preparing for the task, selecting the correct diagnostic procedure, carrying out the diagnosis and the repair, performing post-repair testing, and completing workplace processes and documentation.

It applies to those working in the automotive service and repair industry. The steering systems include those in light vehicles, light commercial vehicles or outdoor power equipment.

Mechanical - Light Vehicle

Unit Sector

Elements and Performance Criteria

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Diagnose and repair light vehicle steering systems

2.2 Hazard identification and risk assessment .......................................................... 3

2.2.1 Safety precautions while working on steering systems ...............................................3

2.4.1 Personal safety ...................................................................................................................7

2.4.2 Tools and equipment safety ............................................................................................9

3.2 Sources of information for vehicle inspection .................................................. 15

3.3 Selection of tools and equipment .................................................................... 18

4.2.1 Caster ................................................................................................................................ 23

4.2.2 Camber............................................................................................................................. 24

4.4.2 Steering columns ............................................................................................................. 29

4.4.3 Clock springs .................................................................................................................... 30

5 Manual steering system .................................................................................. 33 5.1 Rack and pinion systems.................................................................................... 33 5.1.1 Principle ............................................................................................................................ 33 5.1.2 Operation ......................................................................................................................... 34 5.2 Steering boxes .................................................................................................... 35 5.2.1 Rack and pinion steering boxes................................................................................... 35 5.2.2 Manually operated Rack and pinion assembly ....................................................... 36 5.2.3 Recirculating ball steering system ............................................................................... 36 5.2.4 Steering variable ratio .................................................................................................... 37 6 Hydraulic power steering systems ................................................................ 39 6.1 Operating principle ............................................................................................ 39 6.2 Components of power steering ........................................................................ 39 6.2.1 Power steering pump ..................................................................................................... 40 6.2.2 Power steering pump drive belts ................................................................................. 40 6.2.3 Electric power steering .................................................................................................. 41 6.2.4 Flow control and pressure relief valves ....................................................................... 41 6.2.5 Power steering gearbox ................................................................................................ 41 6.2.6 Power steering hoses ...................................................................................................... 42 6.3 Types of power steering systems ....................................................................... 43 6.3.1 Integral piston system ..................................................................................................... 43 6.3.2 Power assisted rack and pinion steering system....................................................... 44 6.3.3 Operating principle at different steering wheel positions ...................................... 44 6.4 Electronically controlled power steering systems ............................................ 45 6.4.1 Four-wheel steering ........................................................................................................ 46 6.4.2 Steer-by-wire system ....................................................................................................... 46 7 Electric steering systems ................................................................................. 48 7.1 Electrically powered hydraulic steering ........................................................... 48 7.2 Electrically assisted steering ............................................................................... 49 7.3 Electric power steering system .......................................................................... 49 7.4 Steering angle sensor ......................................................................................... 50 8 Diagnostic testing procedures for light vehicle steering systems.......... 51 8.1 Operational testing for hydraulic power steering system ............................... 51 8.2 Inspecting the fluid leakages ............................................................................ 51

8.4 Power steering fluid pressure test ...................................................................... 53

8.5 Diagnosing of steering faults ............................................................................. 54

9.3.1 Steering rack overhaul ................................................................................................... 58

9.3.2 Tie rod end replacement .............................................................................................. 61

10 Final procedure of vehicle servicing ........................................................... 68

10.1 Road test ......................................................................................................... 68

11 References ........................................................................................................ 75

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Figure 1: Steering wheel in a vehicle

Steering systems are also designed to –

ADR 10 – The function of this Australian Design Rule is to minimise crushing or penetrating injuries to drivers due to the ‘steering column’ as a result of frontal impact.

As vehicle technology has progressed, steering systems have gone through a number of refinements to enhance vehicle safety, handling, and even fuel economy.

Work health and safety (WHS) govern the safety, health and well-being of people involved in work or employment. Irrespective of the nature of work, employees must be able to carry out their responsibilities in a safe and secure working environment which is free from hazards.

Figure 2: Work health and safety

•involve employers, employees and the organisations that represent them in the formulation and implementation of health, safety and welfare standards.

WHS play an important role in providing a safe workplace for both employers and employees.

Diagnose and repair light vehicle steering systems

2.2.1Safety precautions while working on steering systems
•When working with steering systems, always wear correct PPE such as safety glasses and gloves, and beware of high pressure and hot oil.

•During the bleeding operations, the steering should not be held on full lock for more than a few seconds at a time.

•Never remove key from ignition while vehicle is in motion as the steering system will lock and steering of the vehicle will cease

•Always use appropriate tools while removing steering system components

2.2.2Safety while working on high pressure and high temperature steering systems

The fluids and oils used for the steering system are very hazardous and leads to irreversible damages. It is important to use proper kind and well-known brand of steering fluid.

•Control on steering is lost because of high pressure and temperature which results in accidents.

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•Different fluids react differently to pressure and temperature changes. Using the incorrect fluid may result in the creation of excessive pressure within the system, bursting the high-pressure lines and potentially spraying fluid at high pressure all over the engine, creating a severe fire hazard. It would also cause a loss of steering assist, which could result in an accident.

Safety measures also include –

•The power steering fluid must be cleaned up immediately as it is considered as a fire hazard.

Figure 4: Sample power steering fluid

Diagnose and repair light vehicle steering systems

•Ensure that the PPE such as overalls, goggles and ear muffs are always worn when using air-powered equipment.

2.3 Environmental requirements
Trap
Always collect the waste and contaminated power steering fluid in an approved container.

Label must be clearly placed on all waste oil and fluid materials
2.4Safety
In the automobile service, it is very important to follow the safety practices as we work with many hazards, some are expected and some are not expected. So, one working on the diagnosis of vehicle should be capable of risk assessment and risk management.

The types of personal protective equipment are below listed ones:

PPE	Purpose	Image
Safety helmets	To protect from any head injury or impact or penetration

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Diagnose and repair light vehicle steering systems

2.4.2Tools and equipment safety
An automotive technician must adhere to the following shop safety guidelines when using tools and equipment.

•Inspect the tools for the cracks or damages and never use the tool if found faulty. •Use the appropriate tools for the purpose they are designed.

•Be careful when using sharp or pointed tools.

•Do not place sharp tools or other sharp objects into pockets.

•Check the wiring for insulation cracks, as well as bare wires, before using it. •Avoid contact with electrical tools using wet hands and water surrounding as it leads to electrical shock. Also, when using electrical power tools, never stand on a wet or damp floor.

•Before plugging in an electric tool, make sure its switch is in the off position. •Always turn off the tool before unplugging the tool.

Figure 8: Diagnosing vehicle with electric tools •Never leave a running power tool unattended.

d)Compressed air tool safety
Power tools that use compressed air are called pneumatic tools.

•Pneumatic tools must always be operated at the pressure recommended by the manufacturer.

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