Power steering pump failure on HGVs: symptoms and replacement
The power steering pump on a heavy commercial vehicle is a vane or gear pump driven by the engine via a belt or direct drive from the timing gear. It pressurises hydraulic fluid and supplies it to the steering gear, which amplifies the driver's steering input. Without functioning power assistance, a fully laden HGV is extremely difficult to steer at low speed.
The most common failure mode is internal wear causing a drop in pump output pressure. This shows as heavy steering at low speed. A pump that is failing will often produce a whining noise that increases with engine speed and is louder on full lock. Before condemning the pump, check the fluid level and condition, the drive belt tension, and any external hose connections for leaks or restrictions.
Frequently Asked Questions
How do I know if my HGV power steering pump has failed?
Heavy steering at low speed or when manoeuvring, a whining noise from the pump that is speed-related rather than load-related, and foam or discolouration in the power steering reservoir are the main indicators. Check fluid level and hose integrity first before testing pump output pressure.
Can a power steering pump be reconditioned rather than replaced?
Reconditioned power steering pumps are available and can be a cost-effective alternative on older vehicles. Ensure the exchange unit is rated for the same output specification as the original. Fitting an underpowered unit will result in heavy steering under maximum load conditions.
What fluid does an HGV power steering system use?
Most European HGV power steering systems use a mineral-based hydraulic fluid, typically ZF Lifeguard or an equivalent specification. Check the vehicle handbook for the specified fluid type and do not mix different fluid types. Some newer systems use ATF.
Does Truckstop Group stock power steering pumps for all HGV makes?
We stock power steering pumps for DAF, Scania, Volvo, MAN, Mercedes-Benz, Iveco, and Renault. Call us on 01527 598 000 with your chassis number to confirm the correct pump for your application.
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