Air present in fluid.

Inspect and bleed the system.

Refer to Power Steering System Bleeding

Fluid is low due to improper initial fill or system leak.

Inspect and fill the system.

Refer to Checking and Adding Power Steering Fluid

The pump mounting is loose.

Torque the pump mounting to proper specifications.

Refer to Power Steering Pump Replacement

The power steering gear inlet (pressure) hose is grounding out.

Check and adjust for proper mounting and clearance.

Refer to Power Steering Pressure Pipe/Hose Replacement .