There is air in the power steering fluid.

1. Inspect the power steering system for leaks. Refer to Power Steering Gear and Pump Leaks .
2. Bleed the power steering system. Refer to Power Steering System Bleeding .

The fluid level is OK but still foams.

1. Remove the power steering pump.
2. Inspect the soft plug for cracks.
3. Inspect the housing for cracks. Refer to Power Steering Pump Disassembled View .
4. Replace the power steering pump. Refer to Power Steering Pump Replacement

The power steering pump is leaking internally.

Inspect the power steering pump for leakage.

Refer to Power Steering Gear and Pump Leaks .

Replace the power steering pump. Refer to Power Steering Pump Replacement