GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 1998 🢒 GMC P42 Commercial Chassis 🢒 Engine 🢒 Engine Mechanical - 6.5L 🢒 Power Steering System Bleeding

Power Steering System Bleeding Process

Bleed the air from the power steering system before operating the vehicle whenever you remove or disconnect any of the following components:

    • The power steering pump
    • The power steering gear
    • The power steering oil lines

If you allow air to remain in the power steering fluid system, noisy and unsatisfactory operation of the system may result. Perform the following steps in order to bleed air from the hydraulic system:

    Important: When bleeding the system, and any time fluid is added to the power steering system, only use power steering fluid as specified in Fluid and Lubricant Recommendations .

  1. Ensure that the ignition switch is in the UNLOCK position.
  2. Turn the steering full left.
  3. Fill the power steering fluid reservoir to the FULL COLD level. Leave the cap off.
  4. Raise the front wheels off the ground and support the vehicle using suitable safety stands.
  5. Place a drain pan under the vehicle in order to catch any power steering fluid that may overflow.
  6. With an assistant inspecting fluid level and condition, turn the steering wheel lock-to-lock at least 40 times:
    7. • Trapped air may cause the fluid to overflow. Any fluid that spills out will need to be cleaned off of the outside of the reservoir in order to allow for a proper leak check.
    • Maintain the fluid level at FULL COLD.
    • Fluid should be free of any air bubbles. If any air bubbles are present, inspect all of the power steering hose fittings for leaks. Repair any leaks, and repeat step 6.
  7. Start the engine and allow the engine to idle.
  8. Maintain the power steering fluid level at FULL COLD.
  9. Install the power steering reservoir cap.
  10. Return the front wheels to the straight ahead position.
  11. Lower the front wheels to the ground.
  12. After allowing the engine to idle for 2 minutes, fully turn the steering wheel in both directions in order to verify the following:
    13. • Smooth power assist
    • Noiseless operation
    • Proper fluid level
    • No system leaks
    • Proper fluid condition (no air bubbles, foam, or discoloration)
  13. If any of the conditions remain, refer to Special Conditions in this section.

Power Steering System Bleeding Special Conditions

Foam or Bubbles in the Power Steering Fluid
    • The power steering fluid must be completely free of bubbles.
    • Bubbles in the fluid indicate a loose connection or a leaky O-ring seal.

Discolored Fluid (Milky, Opaque, or a Light Tan Color)
    • If the power steering fluid is discolored, wait 2 minutes, then recheck the hose connections.
    • Refer to Power Steering System Bleeding and repeat steps 7-11. If the conditions exist, replace the O-ring seals, refer to "End Plate and Rotating Group Replacement" in Power Steering System.
    • Fill the system and repeat the bleeding procedure.

Noise (Pump Whine or Groan)
  1. With the engine running, inspect the hoses for possible contact with the frame, body, or engine.
  2. Allow the system to cool if no contact is found.
  3. After cooling, restart the engine and allow the engine to idle for 2 minutes in order to allow the system to heat up to operating temperature.

    4. Replace the power steering pump if the noise is still present. Refer to Power Steering Pump Replacement .

  4. Repeat the bleeding procedure.