There is air in the fluid or a loss of fluid due to an internal pump leak.

1. Repair the leak.
2. Bleed the system. Refer to Power Steering System Bleeding .

Extremely cold temperatures cause system aeration if the oil level is low.

The reservoir line has hose or air leakage.

1. Repair the leak.
2. Bleed the system. Refer to Power Steering System Bleeding .

Extremely cold temperatures cause system aeration if the oil level is low.

The oil level is correct but the pump foams.

1. Remove the pump from the vehicle.
2. Separate the housing from the reservoir.
3. Inspect the welsh plug and the housing for cracks.
4. Replace the housing if the plug is loose or the housing is cracked.