Checklist: Power Steering Diagnosis – How to Check the Steering Rack

One crucial characteristic of any car is its handling and safety. These two points are closely connected because it is unsafe to drive a car that poorly responds to steering input or has more serious malfunctions. Every car has a steering system, but the type and construction may vary. While steering gearboxes were previously used for turning the wheels, cars with gearboxes are becoming less common. Modern models often employ steering systems where the primary component is the steering rack.
Steering systems are divided into three main categories:
Without power steering;
With hydraulic power steering (HPS);
With electric power steering (EPS).
The first type is straightforward – the driver turns the wheels with purely muscular force. Now, let's delve into the other two types.
Hydraulic Power Steering (HPS)
HPS systems operate by pumping hydraulic fluid and distributing it based on the direction of wheel rotation. They consist of three main components:
Steering Rack: This includes the housing, steering rack bar, and distributor. The distributor and rack bar form a worm gear: when the driver turns the steering wheel, rotational movements are transmitted through the steering column shaft to the distributor. The distributor engages with the teeth of the rack bar, which can move left or right. The task of the steering rack is to convert rotational movements into reciprocating movements. The rack bar is connected to the wheels through steering rods and tie rod ends, which pull/push the wheels in the desired direction.
Steering Column: The column is an intermediate link between the steering wheel and the rack. The design of these mechanisms can vary, but the essence is the same – it is a shaft or several shafts connected through small universal joints.
Power Steering Pump: The HPS pump can be considered a distinctive feature of such systems. Its purpose is to create hydraulic pressure in the system and deliver it through hoses to the steering rack distributor. Depending on the direction of wheel movement, the distributor directs the oil to the appropriate chamber of the rack, thereby easing the driver's effort. HPS pumps are powered by a belt through a pulley, meaning the unit operates when the car's engine is running.
There are also hydraulic pumps with electric drive, where an electric motor replaces the internal combustion engine. This type of power steering is called Electric Hydraulic Power Steering (EHPS).
Electric Power Steering (EPS)
In EPS, there is also a steering rack and column, although their design may differ. The main difference lies in the power assist, which is an electronic control unit, sensors, and an electric motor. This motor is connected to the rack bar and helps it move in the desired direction. The direction of rotation of the electric motor and the degree of assistance are determined by the Electronic Control Unit (ECU), which calculates based on sensor data.
Neither of the listed systems can work forever, so repairs will be needed over time. However, before repairing, a quality diagnosis must be performed to accurately identify the problem and "not treat a healthy system."
Car Steering System Diagnosis
The direction of the search for faults depends on the driver's complaints and the type of power steering. In any case, accurate steering system diagnosis is impossible without two crucial points: it should be carried out by a qualified specialist equipped with specialized tools and equipment.
Let's go through some common complaints and diagnostic methods:
Knocking: Knocking from the rack during movement over bumps or when turning the steering wheel is the most common complaint. The causes of knocking can be several: wear of the rack sector gear, misadjustment of the rack (rack bar preload), bushing wear, wear of the universal joints on the column shaft, etc.
For diagnosis, a specialist:
Lifts the car on a lift;
Visually inspects the rack and dust boots, checking for any damage or poor fixation;
Removes the dust boots, visually inspects the rod with the wheels turned in different directions;
Mechanically shakes the steering rack bar in various positions to find the cause and determine the extent of the problem;
Checks the backlash of the universal joints. The backlash can be the cause of knocking and a feeling of "sticking" or loss of power assist.
If the problem is not found, further diagnosis of the car's suspension may be required.
Reduced Hydraulic Fluid Level in the Reservoir, Fluid Leakage: Leakage can occur in different ways. Sometimes car owners report a leak they have already discovered independently. However, the leakage site is not always obvious, and it is not easy to find it quickly. The reduction in the fluid level in the reservoir indicates a problem.
For diagnosis, a specialist:
Checks the entire hydraulic system for leaks, starting from the pump and hoses to the rack and dust boots;
Inspects the rack and dust boots visually to identify any damage or poor fixation;
Removes the dust boots, visually inspects the rack bar in different positions of the wheels;
Checks the hydraulic fluid level in the reservoir.
In both cases, further disassembly of the system, inspection, and, if necessary, replacement of worn parts will be required. After repair or replacement, a test drive and additional steering system diagnostics may be necessary to ensure that the problem has been successfully resolved.
In conclusion, it is essential to address any issues with the steering system promptly to maintain the safety and optimal performance of the vehicle. Regular maintenance and timely diagnosis by qualified specialists are key to identifying and rectifying steering system problems.
The check is performed as follows:
Inspect the reservoir for any damage.
Visually check the power steering pump. Leakage may occur if the sealing rings are no longer performing their tasks.
Inspect the steering rack, focusing on connections, housing, and dust boots, as leaks are most common in these areas.
If all previous points are in order, proceed to check all hoses and pipes. Some vehicles may have design flaws that cause pipes to wear out. Occasionally, a hose or pipe may be unfixed due to an assembly error from a previous repair.
3. Power Steering Failure or Incorrect Operation
In this case, the diagnosis procedure depends on the type of power steering system.
Electric Power Steering (EPS) Diagnosis:
EPS diagnosis involves connecting diagnostic equipment and a computer with specialized software to the rack. A specialist conducts the diagnosis and reads error codes.
Sometimes, reconnecting a detached connector is sufficient after identifying the cause. However, more often, the rack with the power assist is removed from the car and sent to the workshop for further diagnosis and defect identification.
Hydraulic Power Steering (HPS) Diagnosis:
Check the condition and tension of the drive belt. If the belt breaks, the driver will notice it. However, reduced tension can lead to unstable operation not only of the power steering pump but also of the air conditioner compressor and the alternator. The reason is belt slippage on the pulley without rotation. A slipping belt heats up and can break. An overtightened belt is also undesirable as it increases the load on the bearings of the driven components.
Check the fluid level and its condition in the reservoir. Drivers may not always notice a decrease in the reservoir level. Insufficient fluid can cause jerky system operation, harming the pump due to inadequate lubrication. If there is a fluid level problem, the technician moves on to searching for leaks.
Measure the pressure in the HPS system using specialized equipment. It is possible that the problem lies in the pump itself, and it is not generating the necessary pressure for stable system operation. This measurement is crucial for diagnosis.
If the pressure measurement shows low values, the pump is removed and sent for disassembly and inspection. Depending on the diagnosis results in the workshop, repair or replacement of the unit may be required.
4. Steering Wheel Binding or Failure to Return to Neutral Position
It's important to note that the steering wheel may not return to the neutral position after turning due to incorrect wheel alignment angles. If this is the case, the problem may be resolved with a wheel alignment.
Steering binding may occur after hitting a deep pothole, striking a curbstone, or after a collision.
Diagnosis for Steering Binding:
The technician attempts to determine the position causing the binding by turning the steering wheel.
Inspect the universal joints for play. High play indicates wear on the cross, which can lead to binding.
Remove the dust boots from the tie rods, inspect the rack bar for bends. If bending is present, only replacement of the rack bar or the entire assembly may help, as finding a specific rack bar for certain rack models can be difficult or impossible.
If the problem is not found, the rack is removed from the car and sent to the workshop for further defect identification. The issue may be with the distributor or rack bar teeth, which cannot be determined on the vehicle.
Case: Repair of the Audi A4B8 Steering System
An Audi owner complained that the power steering, in their perception, does not always engage when turning the wheel. However, when it works, it does so consistently. Computerized diagnostics did not reveal any issues, and there were no dashboard errors. Let's find out what happened.
The technician lifted the car and began diagnosing the rack:
Checked for play.
Inspected dust boots and the rack bar.
Checked connector connections to the EPS.
No issues were found. The specialist then examined the universal joint, and everything became clear: the cross was worn out and had significant play.

After agreeing on the work with the car owner, the master removed a part of the shaft with the universal joint, replaced the cross with a new one, and reinstalled it. Following this, the play disappeared, and along with it, the power steering system returned to stable operation.
Increased play in the universal joint of the shaft led to initial "free play" when turning the wheel, causing the power steering not to engage, and the wheels not to turn. After replacing the universal joint, the system functioned properly and predictably.
For more of our steering system repair work, check out our portfolio.
Where to Conduct Steering Rack Diagnostics?
The car's steering system significantly influences comfort and safety while driving. Like all other components in a car, it has a lifespan that can be reduced due to insufficient maintenance, damage to dust boots, or other unpredictable issues.
To ensure the rack, column, and power steering operate correctly and last a long time, it's essential to periodically visit a specialized service center and undergo preventive inspections. These inspections help prevent breakdowns or address existing problems at early stages.
However, if you've already noticed issues, it's crucial to promptly visit an auto repair shop where specialists work with the necessary diagnostic tools and equipment. Professional diagnostics will accurately identify the true cause of the malfunction and address it without interfering with the functional components.
STS specialists have been involved in diagnosing and repairing car steering systems for over 20 years. During this time, we have become experts not only in repairs but have also developed diagnostic equipment for power steering rack diagnostics with power assistance (HPS) and electric assistance (EPS), which we use in our work.
Our experience has helped us create our own brand of steering racks, MSG, which is highly respected by customers for its optimal combination of price and quality.
At our warehouse, there is always a wide selection of units and components for high-quality repairs. If your rack is beyond repair, our specialists will suggest suitable replacement options: either an original new unit or a refurbished rack. We restore assemblies using high-quality components, providing you with a practically new rack at a more favorable price.