Replacement of Bosch steering systems

Steering systems are especially safety-relevant vehicle components. Therefore, Bosch says its steering systems have to meet high requirements concerning both quality and reliability. They are mostly maintenance-free and designed to last for the complete vehicle life cycle.

Of course, attachment parts such as tie rods and bellows can be damaged or worn out and should then be replaced. However, complete steering systems usually only need to be replaced in the event of an accident or mechanical overloads affecting the steering function.

When to replace a steering system
According to Bosch, steering systems must be replaced if:

• Clear signs of faults and damages become apparent. This includes unusual noises, hydraulic leakages as well as increased and irregular efforts required to perform steering operations
• There are any visible damages to the steering gear, including housing blackening or discolouration caused by overheating
• The connectors on the control unit of vehicles equipped with electric steering systems (EPS) are damaged or if they have any hairline cracks
• There are lasting deformations or cracks on surrounding or connected components.

In addition, steering systems should also be replaced in case of doubts regarding their proper functioning due to past mechanical overloads. This is usually caused by exterior influences such as accidents or driving maneuvers with extreme forces acting on the steering system.

Besides obvious symptoms, this can also result in hidden damage to mechanical components of the steering gear assembly remaining undetected by driver at first. It is extremely difficult for automotive workshops to perform diagnoses regarding internal damages of steering gears. This is because only the manufacturers are able to perform a proper check on force-transmitting internal components of rack and pinion steering systems.

Possible damages can only be derived indirectly – for instance analysing of surrounding components. Whenever damage to the steering system cannot be excluded, the system should be replaced.

When working on steering systems, comprehensive visual and functional inspections are always the first step. For this purpose, operating forces, resetting, clearances, noises and the warning lamp are checked.

Bosch says workshops using its ESI[tronic] software will find comprehensive service and installation instructions included within the SIS module. They provide information concerning troubleshooting on electrical and mechanical systems. Afterwards, an additional in-depth diagnosis is performed to determine whether a steering system needs to be replaced or if it can be repaired.

The following points should always be observed:

• Install the steering system exactly as described in the installation manual
• Only use attachment parts such as tie rods, bellows and mounting clamps approved by the manufacturer
• Install all attachment parts properly as to prevent consequential damages such as corrosion
• Make sure the warning lamp turns off and the fault memory is cleared after the installation
• Last but not least, perform a test ride on nonpublic grounds to check the steering system’s proper functioning.

Hydraulic steering systems
Bosch advises that only hydraulic oils approved by the manufacturer should be used. When maintaining hydraulic steering systems, flush the system and, if required, replace the fine-mesh filter as well. Once the steering system has been replaced, make sure to fill and bleed it properly.

Electric steering systems
Most electric steering systems need to be parameterised once they have been replaced. The parameterisation can be done via software update using an appropriate diagnostic tester. Bosch uses the example of its DCU 220 with KTS 560/590) or via OEM portal (“PassThru”).

Calibrate the steering-angle sensor using an appropriate diagnostic tester, such as a Bosch tester or an original one.

Before setting the software end stops, it might be necessary to reset preset values using a diagnostic tester. Software end stops are set driving slowly (5-10 km/h) or on turntables.