The power steering pump is one of the most important components of the power steering system. If the component is defective, steering assistance is sometimes no longer available. But other problems can also occur if the component fails. Our guide on the subject of the power steering pump answers many questions and lists signs and causes of a defect.

Function of power pump and power steering

Power steering makes driving a car much easier. That is why almost all modern vehicles today have power steering. The modern steering power assistance reaches under the arms of the driver of the car, so to speak, and facilitates the steering process. For this purpose, the steering device amplifies the steering force depending on how the driver turns the steering wheel.

Steering assistance hydraulic or electric

Depending on the vehicle model and steering system, power steering can be a hydraulic or electric component. Undoubtedly more modern is the electric power steering, where electric motors determine the steering movements.

Hydraulic steering is standard

However, a hydraulic power steering system is still installed in most vehicles today. Here, a hydraulic system with hydraulic oil and a pump provides the necessary steering assistance. This so-called power steering pump, or simply servo pump, is driven either by the V-ribbed belt or electrically, depending on the vehicle model. It provides the necessary pressure.

Typical symptoms of a defective servo pump

Typical symptoms often occur in connection with a defective power steering pump. If the pump is not functioning properly, the power steering will also no longer work properly. The driver often has to use more power for steering when the power pump has failed.

Other symptoms of defective pumps

However, defective servo pumps do not always cause the complete failure of steering systems. Sometimes the malfunction also manifests itself through symptoms such as a change in steering behaviour or a steering gear that feels sluggish. Unusual noises may also occur when operating the vehicle, such as grinding noises or a humming sound when operating the steering.

If servo oil leaks

Sometimes symptoms such as clearly leaking servo oil also indicate a defective servo pump. This can occur due to wear or also due to hardened seals on the pump unit. In this case, the servo pump is also defective. A constant drop in the level of the hydraulic oil or foam in the expansion tank can also indicate a defect.

Symptoms of a pump defect at a glance:

• Steering behaviour in curves is changed
• Increased steering effort
• Oil leaks from the servo pump
• Servo oil level decreases
• Grinding noises from the engine compartment
• Noises like humming when steering
• Foaming in the container for servo oil
• Error message in the on-board computer

Other faults also lead to failure of the steering power assistance system

However, the servo pump itself is not always defective. Particularly with electric servo pumps, a problem sometimes occurs due to corroded connections. This interrupts the flow of current so that the pump cannot build up pressure and the servo does not work. Therefore, a thorough diagnosis should be made before the repair is carried out in the workshop.

Common causes for defective servo pumps

There are various possible causes for a defect in the servo pump. For example, servo pumps are constantly in operation during every car journey and are therefore subject to a certain amount of wear. This is why the pump fails, especially in older cars.

Oil leakage and loads on the servo pump

The servo pump can be damaged by lack of maintenance if, for example, the servo oil has not been topped up. In older models, the loss of oil is often caused by the pump itself. Here, the seals can harden, which leads to the leakage of servo oil. External influences such as mechanical stress or rust caused by winter and damp weather also reduce the service life.

Overview of causes for the defect of the servo pump:

• Wear and tear on older vehicles
• Load in operation
• Servo oil was not refilled
• Ageing of sealing components
• Damage due to external influences

Changing the servo pump

If the power steering pump is broken, the only solution is usually to replace it with a suitable spare part. This is the only way to ensure reliable operation of the power steering system in the future. If you continue to drive with the defective component, the problem can worsen. Steering power assistance can also suddenly fail, which is not without risk depending on the driving situation.

Exchange for a spare part instead of repair

Most modern servo pumps cannot be repaired, so replacement with a suitable new or used part is inevitable. Since a servo pump is not too expensive, repairing the component would rarely be worthwhile anyway.

Work on the steering is a professional matter

All parts of the steering system, such as the steering gear or the power steering pump, are among the safety-relevant components of the car. To be able to change the components, specialist knowledge is sometimes required. Car mechanics with the appropriate expertise sometimes change the power steering pump themselves, otherwise a workshop is the right contact for the change.

Changing the servo pump in 6 steps

Skilled car mechanics are happy to replace the servo pump themselves. In the case of electric pumps for the servo, sometimes only the hydraulic lines and the electrical connections need to be replaced. On the other hand, the replacement of a mechanically driven pump via the V-belt can be more extensive. The exact procedure for changing the servo pump can vary depending on the vehicle model.

Change defective servo pump

1. Prepare to change the pump: In order to be able to repair the power steering, some preparations must be made in advance. As a rule, some trim parts in the engine compartment or other components must be removed in order to have access to the power steering pump. Depending on the vehicle model and the position of the pump, the bumper or one of the front wheels must be removed.
2. Dismantle the V-belt and connections: As part of the power steering system, the power steering pump is driven by the V-ribbed belt in many vehicle models. Therefore, the belt must be slackened before removing the power steering pump. This is done in different ways depending on the model. The connections for the servo oil must also be disconnected or dismantled from the pump unit. Any escaping oil must be collected in a suitable container.
3. Removing the defective servo pump: Once the V-ribbed belt and the connections have been removed, the servo pump can be removed. As a rule, various screws must be loosened before disassembly. The servo pump can then be removed from the engine compartment.
4. Assemble components to new servo pump: Depending on the design of the pump unit and the scope of the parts supplied, some components must be transferred from the old component to the intact replacement part. This is usually the belt pulley, which ensures the connection to the V-belt. The pulley must be detached from the defective pump unit and then attached to the replacement pump.
5. Installing the power steering pump: Once the power steering pump unit is complete, it can be installed in the car. To do this, mount the unit in the intended position and connect the lines. Sometimes it is a good idea to use new screws for this. The V-ribbed belt, once slackened, can also be replaced with a new one if necessary. The belt is carefully fitted and tensioned after the servo pump has been installed.
6. Complete the repair: To complete the repair, the power steering system is filled with new power oil and bled. The new pump unit can then be tested for function and a test drive undertaken to assess the steering power assistance. The level of the hydraulic oil must subsequently be checked again.

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