There is air in the power steering fluid.

1. Inspect the power steering system. Refer to Power Steering System Test .
2. Bleed the power steering system. Refer to Power Steering System Bleeding .

There are air bubbles in the fluid.

1. Inspect the ambient temperature for an extremely cold temperature.
2. Inspect the power steering fluid level. Refer to Checking and Adding Power Steering Fluid .

The fluid level is OK but still foams.

1. Remove the pump.
2. Inspect the soft plug for cracks.
3. Inspect the housing for cracks.
4. Replace the pump as needed. Refer to Power Steering Pump Replacement .
5. Replace the housing as needed. Refer to Steering Gear Replacement .

The PS pump has an internal leak.

Inspect the power steering pump for leakage.

Refer to Power Steering System Test .