When a car is not steering properly there can be many possible causes. Power steering specialists need to complete a series of checks to establish the cause of any steering faults before attempting any repairs.
The Test Drive
Most power steering problems can be found on test drives. The technician is listening for any unusual sounds (such as whines or clunks), and also feeling for any unusual feeling in the steering (such as pulling to one side, feeling heavy or spongy). These symptoms can give the technician an idea of where the problem is located in the system.
The On-Ramp Centring Test
The On-Ramp Centring Test involves gently cruising around a curve or on a roundabout and releasing light pressure on the steering wheel to test how readily the steering self-centres. If the steering does not return to centre correctly but instead trails off in one direction or the other then it indicates a problem with the rack, column or a faulty alignment as opposed to a problem with the pump.
The Lock-to-Lock Resistance Check
The Lock-to-Lock Resistance Check is used to test for any stiff spots, any feeling of notchy operation, or any unequal resistance through the lock-to-lock cycle. Any of these symptoms would indicate that there is wear to internal components of the rack, or that there are binding joints somewhere in the steering system.
The Static Parking Load Test
As a technician, stand over the car, engine running, and lock up the steering wheel to both the left and right lock and hold for a brief moment. If it required significantly more pressure to lock the wheel than normal the pump pressure is likely low. This test is often referred to as a static parking load test and is typically used as part of the normal diagnostic procedure for both hydraulic and electric-assist powered steering systems. There is more on power steering specialists at https://westernpowersteering.co.uk/.
Electronic and Hydraulic Pressure Measurement
In hydraulic systems, a pressure gauge is attached in-line to the pump. On electric power steering systems, the technician can use a diagnostic reader to pull information from the torque sensor and motor as needed to confirm the numbers against specifications for hardware.
A full test of the steering feel on your car can be completed in under an hour and will ensure the correct repair is carried out first time.
