Whining or groaning when turning
A noise that rises and falls with the engine, loudest at full lock.
Direct causeThe pump is starved, drawing air, or worn internally.
Physical realityThe pump is belt-driven and turning whenever the engine runs, so its noise tracks engine speed rather than road speed. It is loudest at full lock because that is where the system hits its pressure relief valve and flow demand peaks — and holding full lock for more than a few seconds is itself what wears pumps out.
Safety riskLow at first and medium as it progresses. The noise is a warning, not the fault; the fault arrives when assistance goes with the pump.
Required fixFluid level and condition first, then look for aeration, then pressure-test. Replacing the pump before checking for an air leak fits a new pump to the same fault.
What usually causes it
- Low fluid — the cheapest cause and, on a sealed system, always evidence of a leak somewhere.
- Aerated fluid — air drawn in past a return-line clamp or a low reservoir. The fluid looks milky or foamy and topping it up changes nothing.
- Wrong fluid specification — ATF in a system built for synthetic hydraulic fluid, or the reverse, both foam and both are noisy.
- Worn pump — a metallic whine that stays after the fluid is corrected and bled.
- Slipping drive belt — a squeal rather than a whine, worst on a cold start and on initial lock — a different fault with a much cheaper fix.
Diagnostic verification criteria
How a workshop separates these causes rather than replacing parts in sequence.
- Primary indicator: Whether the noise responds to steering input. A noise that changes with lock is hydraulic. A noise that tracks engine speed regardless of the steering is the belt or a pump bearing.
- Tolerance limit: Visible foam in the reservoir with the engine running means air is being drawn in continuously. That is a sealing fault on the suction side, and no amount of fluid corrects it.
- Secondary failure risk: Aerated fluid cavitates and erodes the pump's internal surfaces, so an air leak that costs a clamp to fix becomes a pump if it is left.
RM Steering and Suspension diagnoses and reconditions power-steering pumps in Brackenfell, Cape Town — in-house, rather than defaulting to replacement.
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