Steering System Noise Definitions: Hiss

Hiss or valve hiss is a high-frequency sound coming from the steering gear when the system is loaded. It is a rushing or "swish" noise that does not change frequency with RPM. Hiss is the general noise generated by flow of hydraulic fluid though restrictions in the steering system and typically worsens with increasing temperatures. Restrictions include the rotary steering valve, power steering tubes, connectors, tuning orifices, etc. Hiss can be airborne and structure-borne, but the structure-borne path through the steering intermediate shaft is usually dominant.